Logo - Hellma Materials

General questions about the company

What is the difference between Hellma Materials, Hellma Analytics and Hellma Solutions?

All three companies mentioned – Hellma Materials, Hellma Analytics and Hellma Solutions – belong to the Hellma Group. The main difference lies in their respective product focus and the associated areas of application:

Hellma Materials specialises in the production of high-purity optical materials and crystals. In particular, this includes the cultivation of calcium fluoride, barium fluoride and magnesium fluoride. They also offer specialised materials such as ytterbium-doped calcium fluoride for laser applications, germanium for the IR range and ceramic materials such as zinc sulphide and Cleartran®. Scintillation crystals are also part of their portfolio.

Hellma Analytics specialises in optical components and solutions for analytics. These primarily include cuvettes, optical fibres and other optical components that are used in spectrophotometers and other analytical devices. Its focus is on precise measurements in laboratories and industrial applications.

Hellma Solutions offers customised optical solutions and assemblies. They develop and manufacture optics for specific applications in various industries that go beyond the standard Hellma Analytics range. This can range from the development of complex optical systems to the integration of Hellma components into larger systems.

Does Hellma Materials specialise exclusively in crystal growing?

No, Hellma Materials does not specialise exclusively in crystal growing. Although the focus is on growing high-purity calcium, barium and magnesium fluoride, Hellma Materials also offers other materials. These include ytterbium-doped calcium fluoride for special laser applications, germanium for the IR range and ceramic materials such as zinc sulphide and Cleartran®, which are produced in a separate plant in Louisana. Its portfolio is rounded off by scintillation crystals from the plant in Jena.

For which sectors and industries does Hellma Materials offer products?

Hellma Materials supplies a range of specialised high-tech industries.
The products – in particular synthetic crystals such as calcium fluoride, germanium, zinc selenide or scintillation crystals – are key components for sophisticated optical systems.

The main sectors and industries are:

  • Semiconductor industry: Special optics made from materials such as calcium fluoride are of crucial importance for lithography processes in chip production.
  • Optics and photonics: This is the core industry. This includes the manufacture of lenses, windows and other optical components for lasers, cameras and spectrometers.
  • Defence and security: A very large application area that includes the following technologies, among others:
    • Thermal imaging technology and infrared systems: For surveillance, target acquisition and night vision devices.
    • Aiming optics: For high-precision sights and aiming systems.
    • Sensors and detectors: For the detection and analysis of substances (CBRN defence).
  • Aerospace and aeronautics: For optronic reconnaissance systems in aeroplanes, drones and satellites.
  • Maritime and defence technology (Naval): For periscopes in submarines and for monitoring and targeting systems on ships.
  • Metrology and analytics: In scientific devices such as spectrometers, which require high-purity and precise optical elements.
Where does Hellma Materials produce its crystals and optics?

Hellma Materials produces at several locations in Germany and Sweden:

  • Jena, Thuringia: This is the main location and a central centre for crystal growing and development.
  • Eisenach, Thuringia: IV IR Optics GmbH, which is also active in the field of crystal technology and belongs to Hellma Materials, is based here. Germanium is mainly grown here and prefabricated for customers on CNC machines.
  • Trollhättan, Sweden: Hellma Materials Sweden AB operates crystal growing at this site.
Is there a difference between the production sites in Germany and Sweden?

Yes, it does exist. It is currently only cultivated inSweden. However, the quality of the crystals is absolutely identical, as they are made from the same raw material / starting material, calcium fluoride.

  • Jena, Thuringia: This is the main site and a central centre for crystal growing and processing crystals into semi-finished products for customers.
  • Trollhättan, Sweden: Hellma Materials Sweden AB currently operates a pure crystal growing facility at this site.
Does Hellma Materials also offer products in smaller quantities for research and development?

Yes, of course. As we don’t have an off-the-peg product, every enquiry is in principle OEM or individual and a minimum quantity doesn’t really matter.

How can I contact you for technical advice?

There are two simple ways to obtain technical advice on our products:

Via contact form: Use the contact form on our website. Your enquiry will be automatically forwarded to the right contact person for your specific request.

By e-mail: Send us your technical questions and specifications directly to sales.materials@hellma.com. Our team of experts will get in touch with you as soon as possible.

Questions about optical crystals (e.g. CaF2, BaF2)

What types of optical crystals do you grow?

Hellma Materials grows a range of high-purity, synthetic crystals for various high-tech applications.

These include above all:

  • Fluoride crystals: Such as calcium fluoride (CaF2) and barium fluoride (BaF2), which are used particularly in UV and infrared optics, for laser applications and in the semiconductor industry.
  • Infrared materials: such as germanium (Ge), zinc sulphide (ZnS) and zinc selenide (ZnSe). These are essential for the production of lenses and windows in thermal imaging cameras and other IR systems.
  • Scintillation crystals: Special crystals that are used to detect ionising radiation, for example in medical technology, security checks or research.
What are the main differences between calcium fluoride (CaF2), barium fluoride (BaF2) and silicon (Si)?

An overview of the main differences between calcium fluoride (CaF2), barium fluoride (BaF2) and germanium (Ge), three fundamentally different materials in optics.

The choice of material depends directly on the desired application, as their optical and physical properties are very different.

Summarising overview

FeatureCalcium fluoride (CaF2)Barium fluoride (BaF2)Germanium (Ge)
Transmission rangeVery broad: UV, visible, infrared (approx. 130 nm – 9 µm)Very broad: UV, visible, infrared (approx. 150 nm – 12 µm)Infrared only (approx. 2 µm – 14 µm)
AppearanceTransparent (similar to glass)Transparent (similar to glass)Opaque, grey-metallic glossy
Refractive indexLow (approx. 1.43)Low (approx. 1.47)Very high (approx. 4.0)
Main applications– Lenses for cameras & lithography
– UV & laser optics
– Spectroscopy		– Thermography & heat sensors
– Analytics
– Scintillation detectors
– Thermal imaging cameras (FLIR)
– Infrared optics
– Semiconductor technology
Special properties– Low dispersion (colour error correction)
– Sensitive to temperature shocks		– Slightly more resistant than CaF2
– Is a scintillator (lights up when irradiated)		– High density (heavy)
– Becomes opaque at >100°C (thermal runaway)

The main differences in detail:

  1. Visibility and wavelength:
    • The most fundamental difference: CaF₂ and BaF₂ are transparent to the human eye and allow light from the ultraviolet (UV) to far into the infrared range (IR) to pass through.
    • Germanium is completely opaque to visible light. Its strength lies exclusively in the infrared range, which is why it is the material of choice for thermal imaging cameras. You cannot “see through” it like a glass window.
  2. Refractive index:
    • Fluorides have a very low refractive index, similar to glass.
    • Germanium has an extremely high refractive index. This makes it possible to produce highly refractive lenses with low curvature, which is crucial for compact IR systems.
  3. Application:
    • Fluorides (CaF2, BaF2) are all-rounders for high-performance optics that have to function over a wide wavelength range – from UV applications in the semiconductor industry to infrared spectroscopy.
    • Germanium specialises in a single but very important application: thermography. Almost every thermal imaging camera that visualises body or ambient heat uses germanium lenses.

To summarise, CaF2 and BaF2 are broadband, transparent materials, while germanium is a pure infrared specialist with unique metallic properties.

For which wavelength range are your crystals (e.g. CaF2) suitable?

Our crystals are specialised for different wavelength ranges to cover a wide range of applications. The crystal you mentioned as an example, calcium fluoride (CaF2), is particularly versatile.

Here is an overview:

  • Calcium fluoride (CaF2) and barium fluoride (BaF2): These crystals are characterised by an extremely wide transmission range. They are suitable for applications from the deep ultraviolet (UV) to the entire visible range (VIS) and far into the mid-infrared range (IR). The typical range for CaF2 is approx. 130 nm to 9 µm.
  • Germanium (Ge), zinc sulphide (ZnS) and zinc selenide (ZnSe): These are pure infrared materials. They are opaque to visible light and are used specifically for the medium to long-wave infrared range (approx. 2 µm – 14 µm), which makes them ideal for thermal imaging cameras.
  • Scintillation crystals: These have a different function. They are not primarily intended for light transmission, but for the detection of high-energy radiation such as gamma and X-rays.
What are the maximum dimensions (diameter) in which you can supply crystals such as CaF2, BaF2?

We grew the world’s largest ever crystal of high-purity calcium fluoride in 2021 and it was exhibited at SPIE Astronomical Telescopes + Instrumentation 2022.
This calcium fluoride crystal has a diameter of 620 mm and weighs 200 kg.

© Hellma Materials: World's largest cultivated synthetic calcium fluoride crystal
© Hellma Materials: World’s largest cultivated synthetic calcium fluoride crystal

Here is an overview of the average available sizes of our individual materials / semi-finished products:

  • Calcium fluoride (CaF2): up to 440 mm monocrystalline
  • Barium fluoride (BaF2): up to 360 mm monocrystalline
  • Germanium (Ge): up to 335 mm monocrystalline
  • Zinc sulphide (ZnS): 2400 mm 1200 mm
  • Cleartran®: 900 mm x 800 mm
    Scintillation crystals:
  • CeBr3: 102 mm
  • Ce:LBC:
  • Eu:CaF2: 100 mm
What does the specification “Yb3+:CaF2” mean?

Ytterbium-doped calcium fluoride .

Broken down, this means:

  • CaF2 is the chemical formula for calcium fluoride. This is the host material or matrix of the crystal.
  • Yb3+ is the chemical symbol for the element ytterbium, here in its triply ionised form. The addition “doped” means that small amounts of ytterbium ions have been introduced into the calcium fluoride matrix. This doping changes the optical properties of the calcium fluoride and makes it usable for specific applications
  • Hellma Materials offers ytterbium-doped calcium fluoride especially for laser applications.
How resistant are your crystals to environmental influences such as temperature and radiation?

The resistance of artificial crystals to environmental influences such as temperature and radiation varies greatly depending on the material. Here is an overview of the crystals and ceramics you mentioned:

Crystals for optics

  • Barium fluoride (BaF2):
    • Temperature: Good thermal stability, can withstand temperatures of up to 800 °C in a dry environment. However, moisture can damage the transmission properties in the UV range.
    • Radiation: Highly resistant to high-energy radiation (UV degradation, X-rays and gamma radiation) and is often used as a fast scintillator for such applications.
    • Other influences: High chemical resistance. Minimal dimensional changes due to temperature and pressure fluctuations.
  • Calcium fluoride (CaF2):
    • Temperature: Can be used in dry environments up to 1000 °C. Above 600 °C, moisture can attack the surfaces. Softening begins at 800 °C.
    • Radiation: Good resistance, especially in the deep UV range. CaF₂ is known for its high laser damage threshold in the deep UV range. Also resistant to radiation and ozone.
    • Other influences: Very good chemical resistance to most acids and alkalis. Non-hygroscopic (does not absorb moisture), making it reliable in humid environments.
  • Magnesium fluoride (MgF2):
    • Temperature: Can withstand high temperatures.
    • Radiation: Shows good resistance to electron radiation in terms of the formation of colour centres in the UV range, which makes it suitable for space applications. X-rays can cause absorption in the 0.25 μm range.
    • Other influences: Very resistant to chemical corrosion, laser damage, mechanical and thermal shocks. Harder than CaF2. Minor hydrolysis possible.
  • Ytterbium-doped calcium fluoride (Yb:CaF2):
    • Temperature: Benefits from the good thermal properties of the CaF2 lattice. Melting point of 1418 °C.
    • Radiation: Low non-linear effects under intensive laser irradiation.
    • Other influences: Cubic symmetry, good mechanical properties, low dispersion.
  • Silicon (Si):
    • Temperature: Silicon rubber has excellent resistance to heat and cold. It can be used permanently at 150 °C and briefly up to 350 °C. The brittleness point is -60 to -70 °C, some products even below -100 °C.
    • Radiation: Good weather resistance and UV resistance. Ozone has hardly any effect.
    • Other influences: Good electrical properties, good chemical stability.
  • Germanium (Ge):
    • Temperature: Its electrical resistance drops sharply during crystallisation in a narrow temperature range. Thermal stability is an important aspect of germanium-based phase change materials.
    • Radiation: Less frequently mentioned as an optical material in terms of radiation resistance in optical applications, but it is a semiconductor whose conductivity can be affected by radiation. Germanium whiskers can cause failures in older diodes and transistors made of germanium.
    • Other influences: Brittle, silvery-white.

Ceramics for optics

  • CVD zinc sulphide and Cleartran® (ZnS):
    • Temperature: Cleartran® is modified by a hot isostatic process which results in higher purity and structural homogeneity.
    • Radiation: Low absorption and scattering over a wide transmission range. Suitable for multispectral applications that require a single beam path for several wavelength ranges.
    • Other influences: Chemically inert, non-hygroscopic, high purity, theoretically dense, easy to process.
  • CVD Zinc Selenide® (ZnSe):
    • Temperature: Can be used as an X-ray detector in a wide temperature range up to at least 130 °C. Monocrystalline ZnSe has an extremely low leakage current over a wide temperature range up to 167 °C.
    • Radiation: Good radiation resistance, especially when doped with tellurium. Promising material for X-ray detection that does not require cooling.
    • Other influences: Relatively high effective atomic number, large band gap.

Scintillation materials

  • Cerbromide (CeBr3):
    • Temperature: The light yield of most scintillators is temperature-dependent and decreases at higher temperatures. CeBr3 has a relatively high density and a proportional reaction to gamma rays.
    • Radiation: Shows more or less damage when exposed to high doses of radiation, which can manifest itself as a decrease in optical transmission. This damage is often partially reversible.
    • Other influences: Hygroscopic (must be encapsulated). Short decay time, high light yield.
  • Europium-doped calcium fluoride (Eu:CaF2):
    • Temperature: Robust scintillation crystal with good impact and thermal shock resistance.
    • Radiation: Like CaF2 itself, good radiation resistance. Eu:CaF2 has a low light yield when interacting with high-energy gamma rays due to its low density and low atomic number (Z).
    • Other influences: Good light emission, relatively easy to process, chemically inert, well suited for vacuum applications (very low vapour pressure), low background radiation. Has a sharp absorption band at 400 nm, which partially overlaps with the scintillation emission band.
  • Barium fluoride (BaF2):
    • Temperature: See above under “Crystals for optics”. The emission intensity of the fast component is practically independent of temperature.
    • Radiation: See above under “Crystals for optics”. High resistance to high-energy radiation.
    • Other influences: See above under “Crystals for optics”.
  • Cerium-doped lanthanum bromide chloride (Ce:LBC (Ce:LaBrCl)):
    • Temperature: The light yield is highly temperature-dependent, which must be taken into account when developing detectors.
    • Radiation: Lanthanum bromide-based scintillators are known for their high radiation resistance.
    • Other influences: Appreciated for its high energy resolution and fast response time.

To summarise, fluoride crystals (BaF2, CaF2, MgF2) generally exhibit good to very good resistance to temperature and radiation, especially in the UV range. Silicon and germanium have their specific areas of application, with silicon showing remarkable thermal and weathering resistance. Zinc-based ceramics (ZnS, ZnSe) are known for their broad spectral transmission and good robustness. For scintillation materials, the temperature dependence of light output is an important factor and radiation resistance can vary, with materials such as Ce:LaBrCl generally considered to be more radiation-hardened than, for example, doped alkali halides.

Questions about scintillation materials

What is a scintillation crystal and where is it used?

A scintillation crystal is a material that produces flashes of light (scintillations) when it absorbs ionising radiation (e.g. gamma rays, X-rays, alpha or beta particles). These flashes of light can then be detected by a photomultiplier or a photodiode and converted into electrical signals.

Scintillation crystals are used in a variety of applications, especially where radioactive radiation or other high-energy particles need to be detected, measured or visualised. Typical areas of application are

  • Medical imaging: In positron emission tomography (PET) and single photon emission computed tomography (SPECT), scintillation crystals are used to detect gamma radiation from radiopharmaceuticals in the body and thus create images of organ functions or tumours.
  • Radiation protection and dosimetry: For the detection and measurement of radioactivity in the environment, in work areas or for personal monitoring.
  • Nuclear physics and particle physics: For experiments on the detection of elementary particles and the investigation of nuclear reactions.
  • Geophysics and oil/gas exploration: In the search for radioactive minerals or for mapping rock formations.
  • Security checks: For detecting radioactive material in luggage or freight, e.g. at airports or border crossings.
  • Materials science: Investigation of material structures using X-ray diffraction.
What advantages do crystals such as CeBr3 offer over other detector materials?

Cerbromide (CeBr3) offers a number of advantages over other detector materials, especially traditional scintillators such as NaI(Tl) and also newer materials such as Ce:LaBr3:

  • Very low intrinsic background radiation: This is a major advantage of CeBr3 over Ce:LaBr3 and Ce:LaCl3. Ce:LaBr3 and Ce:LaCl3 have intrinsic radioactivity (mainly due to 227Ac impurities) which can affect the signal-to-noise ratio at low count rates. CeBr3 has a much lower intrinsic background, which significantly improves sensitivity, especially for the detection of special nuclear materials (SNM) and at low activity levels.
  • High light yield: CeBr3 has a very high light yield (approx. 60,000 to 68,000 photons/MeV), which leads to better detection efficiency.
  • Fast response time/decay time: With a decay time of around 17-25 ns, CeBr3 is very fast, which enables precise time measurements and applications with high count rates. It also has no slow components that could distort the signal in other scintillators.
  • Excellent energy resolution: CeBr3 offers good energy resolution (typically about 4 % FWHM at 662 keV), which is better than that of NaI(Tl) detectors. Although Ce:LaBr3 can provide slightly better resolution (about 3 % at 662 keV), CeBr3 outperforms Ce:LaBr3 in certain lower energy ranges (e.g. for plutonium-239 and weapons-grade uranium).
  • Operation at room temperature: CeBr3 detectors can be operated at room temperature, unlike semiconductor detectors such as HPGe, which require cryogenic cooling. This makes them more practical and cost-effective for many applications.
  • High density and effective atomic number: With a density of approx. 5.1 g/cm³ and an effective atomic number of 45.9, CeBr3 is an effective detector for gamma radiation.
  • Good proportionality: CeBr3 shows a good proportionality of the light yield to the energy of the gamma rays, which is important for accurate energy spectroscopy.

Applications in which CeBr₃ is particularly advantageous:

  • Nuclear spectroscopy: For the precise identification and analysis of radioactive materials.
  • Medical imaging (PET, CT): High detection efficiency and localisation of positron-emitting isotopes.
  • Security inspections (baggage and cargo scanning): Identification and differentiation of different materials based on their characteristic radiation signatures.
  • Environmental monitoring: Accurately measure and analyse radiation levels, especially at low count rates.
  • High-energy physics experiments: Precise time measurements and particle identification.
  • Geophysics (Measurement While Drilling – MWD): Real-time measurements of gamma radiation from rock formations.

Although CeBr3 is hygroscopic and requires encapsulation, its advantages in terms of sensitivity, resolution and speed outweigh the disadvantages in many demanding applications.

In which forms are your scintillation materials available (e.g. raw, encapsulated, as a complete detector)?

Standard: Our scintillation crystals are manufactured under strictly controlled conditions according to customer specifications, taking into account their highly pronounced hygroscopicity. The manufacturing process includes measurement of the scintillation properties. Surface: finely ground
On customer request, the flat surface intended for signal detection can be polished.

Raw material (crystal boules): Upon special customer request, we supply scintillation crystals in their raw form.

Encapsulated detectors: In exceptional cases, we offer our scintillation materials in a hermetically sealed capsule for easy and safe handling.

Complete detector systems: We do not offer finished detector systems ourselves.

What criteria should I use to select the optimum scintillation material for my application? (e.g. light yield, energy resolution)

The selection of the optimum scintillation material depends heavily on the specific requirements of your application. There are a variety of materials with different properties. Here are the most important criteria you should consider:

  1. Light yield (light yield):
    • Definition: The number of emitted photons per absorbed energy (typically photons/MeV).
    • Significance: A higher light yield leads to a stronger signal at the photodetector and therefore to better statistical accuracy and improved energy resolution. It is decisive for the sensitivity of the detector.
    • Examples: NaI(Tl) is a reference standard with a high luminous efficacy. Many new materials such as Ce:LaBr3 or CeBr3 even surpass NaI(Tl).
  2. Energy Resolution:
    • Definition: The ability of the detector to distinguish between radiation of different energies. It is typically specified as FWHM (Full Width at Half Maximum) of the peak width at a certain energy (e.g. 662 keV for 137Cs). A smaller FWHM means a better resolution.
    • Significance: Crucial for spectroscopy in order to separate isotopes or different gamma lines from each other.
    • Examples: Ce:LaBr3 and CeBr3 offer excellent energy resolution, which is significantly better than that of NaI(Tl).
  3. Decay Time:
    • Definition: The time required by the scintillator to emit light after excitation. The time constant is often specified for the exponential decay of the emission.
    • Significance: A short decay time is crucial for applications with high count rates where fast signals need to be distinguished (e.g. positron emission tomography (PET) or high-energy physics) in order to minimise pile-up effects and achieve good time resolution.
    • Examples: BaF2 and many organic scintillators have very short decay times (a few nanoseconds). NaI(Tl) is comparatively slow at a few hundred nanoseconds.
  4. Density and effective atomic number (Zeff):
    • Definition: The density of the material (g/cm3) and the effective atomic number, which reflects the average atomic number of the atoms in the material.
    • Significance: A higher density and Zeff increase the probability of interaction with incident radiation (especially gamma radiation via the photoelectric effect) and therefore the detection efficiency. Other criteria are more relevant for the detection of neutrons or alpha particles.
    • Examples: Materials with high Z (such as BGO) are very well suited for gamma detection.
  5. Hygroscopicity (hygroscopicity):
    • Definition: The ability of a material to absorb moisture from the environment.
    • Significance: Hygroscopic materials (e.g. NaI(Tl), CeBr3, Ce:LaBr3) must be encapsulated airtight to prevent damage and loss of performance. Non-hygroscopic materials (e.g. CaF2) are more robust and easier to handle.
  6. Radiation resistance (Radiation Hardness):
    • Definition: The ability of the material to maintain its performance characteristics under long-term exposure to high radiation dose without suffering significant damage or performance degradation (e.g. formation of colour centres that impair transmission).
    • Significance: Important for applications in environments with high radiation exposure (e.g. nuclear power plants, particle accelerators, space).
    • Examples: BaF2 is known for its high resistance to radiation. Some plastic scintillators are more susceptible to radiation damage.
  7. Temperature dependence:
    • Definition: How the light yield and other properties of the scintillator depend on the operating temperature.
    • Significance: Some scintillators are very temperature-stable (e.g. BaF2 in the fast part), while others show a significant decrease in light yield with increasing temperature. This is crucial for use in environments with fluctuating temperatures or when temperature control is not possible.
  8. Wavelength of the emission:
    • Definition: The spectral distribution of the emitted light.
    • Meaning: The emission wavelength should be well matched to the spectral sensitivity of the photodetector used (e.g. photomultiplier tube (PMT) or silicon photomultiplier (SiPM)) in order to ensure maximum signal transmission.
  9. Mechanical properties:
    • Definition: Hardness, brittleness, resistance to mechanical shocks or vibrations.
    • Significance: Important for handling, machining and use in harsh environments.
  10. Costs:
    • Significance: The cost of manufacturing and processing the material can be a limiting factor depending on the application, especially for large detector volumes.
  11. Intrinsic radioactivity:
    • Significance: Some materials contain naturally occurring radioactive isotopes (e.g. 138Lain Ce:LaBr3 or 227Ac impuritiesin some materials) that can cause an intrinsic background. This is critical for applications with very low count rates or for the detection of weak sources. CeBr3 is favourable here.

By carefully weighing up these criteria and tailoring them to the specific requirements of your application, you can select the optimum scintillation material.

Questions about optical components and processing

Do you also produce finished optical components such as lenses, windows or mirrors from your crystals?

Hellma Materials focuses on the cultivation of crystals. …

Which optical glasses (e.g. from SCHOTT) do you offer and in which delivery forms are they available?

We also offer the complete product range of optical glass from SCHOTT. The OPTICAL GLASS STORE
of Hellma Materials GmbH and SCHOTT Advanced Optics is characterised by the fact that you can also buy small quantities (up to 20 kg) from us and that there is no minimum order value.

What are the advantages of CVD materials such as zinc sulphide (ZnS), Cleartran® or zinc selenide (ZnSe)?

Zinc sulphide (ZnS)

The main feature of standard ZnS is its exceptional mechanical robustness and cost efficiency.

  • High hardness and strength: It is significantly harder and more break-resistant than zinc selenide, making it ideal for harsh environments.
  • Environmental resistance: It effectively resists rain erosion, dust and abrasion and is therefore often used for external IR windows on aircraft and in military applications.
  • Good IR transmission: It offers reliable transmission in the infrared range (1-14 µm), especially in the important long-wave infrared (LWIR, 8-12 µm).
  • Cost-efficient: It is considered a cost-effective solution for IR optics.

Cleartran® (multispectral ZnS)

Cleartran® is an improved version of ZnS and offers superior multispectral performance as a key benefit.

  • Wide transmission range: A special post-processing method (HIP) extends the transmission to the visible range (0.35-14 µm).
  • Suitability for multi-sensor systems: It enables multiple sensors (e.g. visible cameras, IR detectors and lasers) to utilise a single optical aperture. This simplifies the system design and reduces weight and complexity.
  • Retention of robustness: It retains much of the mechanical strength and environmental resistance of standard ZnS.

Zinc selenide (ZnSe)

The key advantage of ZnSe is its unbeatable optical performance for high-power lasers and thermal imaging.

  • Extremely low absorption: It has an exceptionally low absorption coefficient at the wavelength ofCO2 lasers(10.6 µm). This is crucial to avoid heat damage and optical distortion in high-power laser systems.
  • Very wide transmission range: It covers a very broad spectrum from visible light to the far infrared (0.5-22 µm).
  • Excellent optical quality: It has very high homogeneity, which is essential for high-resolution thermal imaging systems (FLIR).
  • Easier alignment: As it transmits visible light, it simplifies the alignment of optical systems.

To summarise:

  • ZnS is the first choice when robustness and cost are paramount.
  • Cleartran® is ideal when a single optic is required for visible light and infrared.
  • ZnSe is indispensable when performance in high-power CO2 lasers or image quality in thermal imaging devices is the top priority.
Do you also offer special optics such as axicons or optics made of high refractive materials?

Hellma Materials does not offer special optics such as axicons. Hellma Materials “only” grows crystals and processes them into semi-finished products. The material is selected according to customer specifications, sawn to size and then ground.
Hellma Materials itself does not offer final polishing or surface coating.
However, we can arrange for companies to co-operate with us in this respect on request.

Hellma Materials does not offer optics made from highly refractive materials. Hellma Materials offers a range of optical crystals and materials, including those with a high refractive index. For example, SCHOTT’s product catalogue mentions “high refractive index material”, whereby materials with a refractive index of > 1.7 such as SF 57 and SF 6 are mentioned. Silicon is also listed as a material with a “high refractive index” for IR optics. In addition, materials such as zinc selenide, which has high refractive indices in various wavelength ranges, are mentioned.

Can the surfaces of optics be provided with special coatings (e.g. anti-reflective coating)?

As we do not manufacture optics ourselves, we do not offer this step in the further processing of our crystals. However, on request, we can also arrange for companies to work with us in this area.

Questions about customised products, quality and ordering

Is it possible to have crystals or optics made to my specific requirements (custom-made)?

It is of course possible to have crystals or optics manufactured according to your specific requirements. As a potential supplier of semi-finished products made from inorganic crystals, such as calcium fluoride (CaF2), barium fluoride (BaF2), germanium (Ge) or zinc sulphide (ZnS), this is our core competence and daily business.

From the point of view of Hellma Materials, where every customer is essentially an OEM customer, the cooperation works as follows:

  1. Individual consultation and feasibility analysis:
    • We do not start with a standard catalogue, but with your requirements. Together we discuss your application, the required specifications (e.g. size, shape, tolerances, surface quality, crystallographic orientation) and the material properties that are decisive for your optics. Our experts carry out a feasibility analysis to ensure that your requirements are technically realisable.
  2. Customised production:
    • Based on our decades of experience, production begins with the selection of the high-quality raw material through to the high-quality grown crystals. We ensure that every crystal, regardless of the material (e.g. germanium, calcium fluoride), fulfils exactly the same high quality standards. Once the crystals have been grown, they are precisely processed into blanks or blocks. This is where the specific requirements of our customers come into play to ensure the perfect optical quality and homogeneity for their application.
  3. Quality assurance:
    • Every production step, from crystal growing to finishing, is subject to strict quality controls. We carry out various measurements to ensure that the chemical purity, optical transparency and physical dimensions correspond exactly to your specifications. In this way, we ensure that you receive a product that fits perfectly into your production chain.
  4. Close partnership:
    • Our goal is to build a long-term partnership. We understand that as an OEM customer you need not just a supplier, but a partner who understands and can support your development cycles and production processes. We are prepared to react flexibly to changes in your requirements and to support you in the development of new products.

To summarise, it can be said that “custom-made” is our standard. Your specific requirements are the starting point for our work, and we supply you with exactly the optics and crystals you need for your applications.

What is the process for a customised request?

The creation of a customised optical material begins with your enquiry. You send us your specifications and requirements, which our team of experts carefully scrutinises. We compare your wishes with the possibilities of our production and create a customised offer on this basis. This includes a specific price and a binding delivery date.

How does Hellma Materials ensure the consistently high quality of its products?

To ensure the consistently high quality of our products, we have established a multi-stage process. This includes regular audits in accordance with ISO standards, which guarantee continuous compliance with international standards. In addition, we carry out constant internal checks in our production processes to ensure that every product fulfils our strict quality criteria. A lively exchange with our customers is also important to us, as their feedback flows directly into the optimisation of our production processes. In addition, we fulfil all industry standards to ensure the best possible quality at every stage of production.

Which measuring and testing methods are used (e.g. laser optical laboratory)?

We ensure the high quality of our products through a series of measuring and testing procedures that accompany the entire process from crystal growing to the finished semi-finished product.

During crystal growing:

  • We use special measuring methods to continuously monitor the parameters of the breeding process. These include measuring temperature, pressure and other relevant physical parameters. This enables precise control and ensures consistent crystal quality.
  • In crystal growing, advanced methods such as “in-situ” measurement are also used to record the crystallisation rate and other growth parameters directly in the process.

After crystal growing and during further processing:

In addition, we utilise other industry-standard processes to ensure that the mechanical, thermal and optical properties of the materials meet the highest standards.

The grown crystals and semi-finished products are subjected to extensive testing in our laser optics laboratory. Various laser-based measurement methods are used to check optical properties such as homogeneity, birefringence and other customer-specific parameters.

Can I receive a data sheet or a test report for my ordered material?

In order to fulfil the individual requirements of our customers, we rely on comprehensive quality management. On request, we can provide you with the industry-standard batch documents as standard. These documents document the origin and specifications of the material and form the basis for traceability in your own production.

In addition, numerous measurements and tests are carried out in our production facilities to ensure the quality and homogeneity of the crystals. We use the results of these internal checks to allocate each customer the material that best fulfils their specific application requirements. If you also require specific evidence, such as a test report for laser resistance, we will be happy to prepare this and provide it to you. In this way, we guarantee maximum precision and reliability without burdening you with unnecessary internal documents.

How can I request a quote or place an order?

Request a quote

The process begins with your enquiry, often referred to as a “Request for Quotation” (RFQ). In order to provide you with an accurate and fast quote, we need as many details as possible from you. These include:

  • Technical specifications: Send us a drawing or a detailed description of the desired semi-finished product.
  • Material: Name the material you require (e.g. germanium or calcium fluoride).
  • Quantity: Enter the desired quantity.
  • Application: A brief description of the intended use helps us to better understand the requirements.

Our team of experts will carefully examine your enquiry, compare it with our production options and prepare a customised quotation on this basis. This includes a binding price and a realistic delivery date.

Place an order

As soon as you accept our offer, send us a formal purchase order. This should refer to our quotation and contain all essential information such as article number, quantity, price and delivery address. After receiving your order, we will confirm the order and start production.

With us, you can be sure that every step – from the initial enquiry to delivery – is carried out professionally and transparently.

What are your typical delivery times for standard and customised products?

The delivery time depends on your specific requirements and the availability of our materials. While pure crystal growing takes around three months on average, special requirements for size and shape can extend the processing time. Therefore, the delivery time for customised products may be longer than you are used to for standard items.

Thanks to our comprehensive warehousing and the continuous comparison of stock levels with customer requirements, we can also deliver at short notice. Occasionally, a material is already in stock that happens to meet your specifications and is ready for immediate despatch. In order to optimise delivery times for our customers, we also maintain close relationships with our existing customers and adjust production cycles accordingly.

We always endeavour to keep delivery times as short as possible, but due to the complexity and precision of crystal growing, we may have longer waiting times for certain very specific requests. It is best to contact us directly with your requirements so that we can find the best possible solution for you.