Frequently asked questions

There are a few questions, which have regularly been raised by our customers. They might be of interest to you, as well. We listed them below.

Specifications

What is the linewidth of the laser diodes?

The typical linewidth of our laser diodes is < 3 MHz. It is typically characterized by a self-heterodyne linewidth measurement.

 

What is the typical current tuning range of DFB laser diodes?

The typical current tuning range is specified with +/- 0.5 nm. Larger tuning might be possible. But we neither specify this nor can we guarantee it. If you need a higher tuning range please contact us, we are happy to advise you.

 

What is the typical tuning frequency of your lasers?

Typically it is 10 kHz. Some 10’s of kHz are possible. But with higher tuning frequency the tuning of the wavelength tuning will eventually drop down to zero. At 10 kHz tuning frequency the wavelength responsivity is about 40 % of the CW value.

 

What is the coherence length of your lasers?

The coherence length is > 100 m.

 

What are the dimensions of the active area of the laser chip that emits light?

The dimension of the active area is approx. 4 x 1 µm. It is difficult to draw a line here for measurement, since the area around it (the waveguide) might also contain some light.

 

What is the beam diameter at the output and divergence of your ICLs?

The laser beam divergence as per our data sheet is typically 35 degrees on the slow axis (FWHM) and 55 degrees on the fast axis (FWHM). After collimation the beam diameter varies between 3 and 5 mm in three meters distance. The exact dimensions depend on the individual laser and will be noted in the specific collimation datasheet of your laser after characterization.

 

The ICL datasheet lists a minimum optical power of 1 mW - do you have an estimate of typical power, or a specification for the maximum power?

1 mW is the minimum output power we guarantee when you order an ICL. Typically the power is a few mw higher, especially at high currents. The maximum power is not specified. Higher power may be possible on request.

Operation

What is the safety classification of your laser?

In general, you should neither with your eyes nor with optical instruments look directly into the laser beam. Please note that the emitted laser light is invisible. The classification depends on various factors, like wavelength, packaging (fiber coupling, collimation), operation point etc.

Basis for classification is the DIN EN 60 825-1 norm. Accordingly, our lasers range from class 1 to class 3B, whereas most are classified class 3R. For detailed information you should refer to the respective datasheet. The laser class on the datasheet is only valid for use within the specified operational conditions. If you need further information, please contact us.

 

Can the LDs and ICLs be operated in CW as well as in pulsed mode? Which characteristics, such as output power, can be expected in pulsed mode?

Our lasers are specified for operation in continuous wave mode (our QCLs are pulsed). If a laser can be operated in CW mode it also can be pulsed, but not vice versa. But we do not have any specifications for pulsed mode.

 

I do not know which absorption line I should choose for my application. Do you have any advice?

Have a look at our applications by gas section to compare the specifications of matching wavelengths for various gases. You can also check the HITRAN database.

 

What is the lifetime of your lasers?

Our lasers have a guaranteed lifetime of > 8000 h. But our long experience shows expected lifetimes exceeding 20,000 h.

 

Can I operate the laser beyond max. operating parameters?

You should not try this without advice. The probability that the laser will break down is too high. The warranty expires as well. If you have any questions about the recommended operating parameters have a look at our data sheets or contact us for help.

Housing & equipment

Is the lens wide enough to capture the entire laser light? If it isn't, what happens to the stray light? Is there an absorber in place to catch it?

The beam divergence of our lasers is indicated in the corresponding datasheet. For our interband cascade lasers it is, e. g., typically 35 degrees on the slow axis (FWHM) and 55 degrees on the fast axis (FWHM).

Normally a focal distance of 6 mm from the laser window to the lens is used. This will lead to a smaller beam spot in the distance. But there could be a large amount of stray light which would not be captured by the lens. To avoid this effect, we use these lenses with a focal distance of around 1.7 mm. The lens will be much closer to the laser and we capture > 90 % of the laser light – with most lasers even more than that.

Since there is hardly any stray light there is normally no need for any absorber. However, in some high resolution setups a pinhole may be useful, but it is not installed in our collimation setup.

 

If we purchase the laser without a collimating lens, but decide later that we would like to have the lens, what is the lead time on that piece?

The collimating lens is on stock. The lead time is basically the time of shipment. The collimation itself can be done within 4 working days.

 

What is the collimation lens made of?

We use Lightpath lenses. In the range from 600 nm to 1800 nm they are made of D-ZK3 glass. Beyond 1800 nm they are made of a GeSbSe composed glass, called BD-2. Depending on the wavelength the lenses also get a special coating.

 

Is the lens collimation system designed to take into account the presence of a laser window?

Yes, our collimation system takes window aberrations into account. To optimize the collimated beam profile our calculations are based on the beam divergence angles after the light has passed the window.

 

What is the performance loss of the laser beam after collimation?

After collimation the laser beam should have a loss of max. 10 - 20 % measured at about three meters distance.

 

Can I adjust the lens of a collimated TO5 / TO66 cube in x/y/z axis?

No, the lens is fixed after we collimated it. Do inform us, if you want to adjust the optics. We will adapt our setup and provide you with a tool to modify the z-Axis. Please keep in mind that you lose any guarantee on the collimation in that case. Though you still have warranty on the laser, of course.

Have a look at our compact collimation module. It offers the advantages of a collimated beam with specified beam directions and identical reference. This module is additionally equipped with a heat sink plane and TEC and thermistor, while the laser is protected in a hermetically sealed laser housing.

From which material are the windows made of?

The material of the window depends on the laser wavelength:

- 760 nm to 2700 nm: D263 glass
- 2700 nm to 5200 nm: undoped YAG crystal
- > 5200 nm: ZnSe-window

 

Do you have any information on the transmittance characteristics of D263 glass?

Schott AG indicates a luminous transmittance of τvD65 (d = 2 mm) = 91.7 %.

 

What does "CAP" refer to in the quote?

"CAP" refers to the cap that will be placed onto the TO5, TO66 or TO5.6 housing. The cap is available with or without window. We recommend using a cap with interior AR coating for the TO5 and TO66 headers. Visit our packaging site. In the rubric accessories you will find a description of the available caps.

 

What are the advantages and disadvantages of a cap with window / cap without window?

If you choose the cap without window, you will have a mechanical protection of the laser and avoid optical noise from the window. However, the laser will not be protected from all outer influences. Since the noise introduced by the window is marginal, we strongly recommend using an AR-coated window.

If you choose the cap with window, the laser will be mechanically protected and, very important, hermetically sealed. The laser chip will be protected from any outer influences, such as moisture, oxygen or dust.

Please refer to our packaging section for detailed technical drawings and dimensions of the mountings.

 

Is it possible to order the laser without the window?

Yes, of course, you can order the laser with a cap without window. But you will have to be extremely careful to protect the laser chip from impacts like dust, water vapour or oxygen. That is why we recommend using a window.

We offer AR coated windows for our TO5 and TO66 housings to avoid fringes. In this way, you benefit from the advantages of a hermetically sealed package while having least impact on the laser beam. For the TO5.6 housings there is no AR coating available, the window is just for protection.

How good is the AR coating on the laser window?

The AR coating on the window is always optimized for a certain wavelength range. The covered range is from approx. 760 nm to 2700 nm by a kind of glass named D263. The reflectivity is < 0.5 %.

Do all lasers need to have a temperature control system?

Yes, a temperature control system is essential for the thermal management of the laser. Our DFB lasers guarantee stable wavelength emission at a specified operating temperature. We recommend to actively controlling the laser temperature by installing a temperature control system in your setup.

Please have a look at our TO5, TO66 or SM butterfly and PM butterfly mounts. These packages are equipped with a TEC and NTC. You might also wish to check our TO5 and TO66 heatsinks. They facilitate the heat removal and provide connectors for laser diode driver and temperature controller as well as M6 threads for optical posts. You can use them with any standard cage system. To compare the various packages visit our packaging site.

 

For which wavelengths are SM and PM fiber coupled butterfly packages available?  

SM fiber coupled lasers are available from 760 nm to 2360 nm.

PM fibers with integrated isolators are available for the following wavelengths:

1064 ± 5 nm
1238 ± 5 nm
1330 ± 5 nm
1392 ± 5 nm
1510 – 1590 nm
1654 ± 5 nm
1742 ± 3 nm
1854 ± 5 nm
1877 ± 3 nm
2004 ± 3 nm
2050 ± 3 nm

For further wavelengths please contact us.

 

Do your housings already have an isolator?

Isolators are only required for lasers which are packaged in a PM fiber coupled butterfly housing. PM butterfly packages with integrated optical isolators are available at the wavelengths mentioned above. For further wavelengths please contact us.

 

Why is the butterfly housing not available for lasers beyond 2360 nm?

Currently, we are limited to 2360 nm, because there are no suitable fibers available for larger wavelengths.

 

I already have a laser diode set which includes diode mounts, temperature controller, current controller and detector. Do I need any of the additional laser packaging options in the quotation?

If the mount matches our packaging, you are able to use the existing mounts and drivers.

 

Which driver can I use?

For LDs and ICLs we use the TTC001 and TLD001 system from Thorlabs. We offer them as well and would also set it up for you.

 

Where can I get detectors for your lasers?

VIGO System S.A. or Laser Components GmbH sell good detectors.

 

Do you have drawings of the cage system?

For technical drawings of the cage systems, kindly contact the respective manufacturers. Our datasheet for the TO5 and TO66 heatsinks shows the specifications and dimensions of the cube as well as of the electric connectors and M6 threads.

Service

What should I do if problems with a laser occur and I want to send a laser back?

If you experience any problems with one of our lasers please contact a member of our sales staff. They will give you advice whether and how you can send the laser back to us.

 

Do you have a distributor in my country?

Due to the fact that our products are used all over the world we work together with several qualified partners.

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