Tunable IR Quantum Cascade Laser Sources
GENERAL: QCLs are tunable infrared light sources. They are 'naturally' multi-wavelength Fabry-Perot (FP-QCL) devices unless some mechanism is applied to force the laser to emit at a single frequency/wavelength.
There are two principle ways to force single wavelength operation. The first is to 'write' a grating on the device itself which will force the device to emit at a particular wavelength set by the grating frequency. Tuning is then accomplished over a NARROW frequency/wavelength region by varying the device temperature which in turn varies the index of refraction of the device material and thus varies the optical pathlength with respect to the grating and thus varies the emitted wavelength. This method typically allows tuning over 4 to 10 cm-1. These gratings are refered to as "distributed feedback" mechanisms or DFBs, and a QCL that has such a grating is a DFB-QCL.
The second tuning method is to insert the multi-wavelength Fabry-Perot device into an external cavity which can itself be tuned to promote emission over a spectral region of 10s or even 100s of cm-1. That is, instantaneous linewidth can be << 1 cm-1 and the line can be tuned over the wider region. These are called "EC-QCLs".
Commercial suppliers of EC-QCLs include -
Or you can purchase a DFB-QCL from us (or an FP-QCL too).
(A) OUR DEVICES: Our QCLs are from Alpes Lasers SA in Switzerland. You can visit their web site at www.alpeslasers.com. QCLs are a recent development and Alpes is a principle commercial provider. The following table summarizes the currently available products.
QCLs are generally available from inventory in the wavelength region from 4.2 to 16+ microns. Recent developments lead us to expect that devices at wavelengths as short as 3.2 microns will be available so - please inquire.
For a list by wavelength of room temp PULSED DFB types available for fast (2-3 weeks) delivery, click here.
For a list by wavelength of CW Cryogenic DFB singlemode devices in stock for fast delivery, click here!
At a Workshop on QCL Lasers held in Freiburg, Germany, Alpes made a presentation which documents the then-current state of the art (and which remains mostly valid), click here for a copy. Very informative.
For a reasonably good summary of the Alpes product line and accessories, click here and open our 80+ page brochure. This file includes the "FAQ" below. One stop shopping!
If you have questions, please email or phone us. But we also note that your questions may be ones that have been asked before. For a "FAQ" document, please click here.
QCLs are made on wafers. Each wafer can contains many devices of similar performance (and more that do not work at all - that is "yield" or lack thereof). Alpes has now build QCLs at a number of wavelengths in the 5 to 10+ micron region. We encourage you to ask what wavelengths are available in semi-fabricated form as if one meets your needs it will be less expensive and faster delivery than an entirely new one.
(B) HARDWARE: If you choose not to buy an EC-QCL from one of the supplier mentioned above, you have 2 choices regarding hardware to operate "room temp" QCLs.
(1) Alpes offers a "starter kit" of hardware to stabilize the device temperature at any temp from -30C to +30C and to energize (drive) the device. Details of the "starter kit" are contained in the brochure linked above as well as on the Alpes website.. For the USER MANUAL, CLICK HERE. Call or email for prices.
(2) DO IT YOURSELF: you need a thermoelectric cooler to hold the QCL at the temp required by the wavelength you intend to reach (see individual QCL test data to determine what that might be, but usually it is in the region of -30C to +30C). You need a sealed housing to enclose the cooler and the housing (otherwise there will be condensation) and the housing needs an appropriate window. You need a controller/power supply to run and stabilize the TE cooler. You need a power supply to energize the QCL itself. We leave the mechanics and optics of this to you, but recommend the ILX LDT 5900 as a TE cooler controller and the ILX LDX 3232 as a very suitable QCL power supply. These are of course available from Boston Electronics. Email or phone us for prices etc.
In the wavelength region longer than 4 microns there are two types of tunable semiconductor lasers. These are Quantum Cascade Lasers (QCLs, which operate at on near room temperature or sometimes at cryogenic temps) and Lead salt lasers (Pb-salts, which always require operation at cryogenic temperatures). We now offer ONLY QCLs. As we see it, Pb-salt lasers are "dead": something one would use in few situations and fewer soon. With the advent of external cavity QC lasers by Block Engineering, Daylight Solutions and Pranalytica (which provide a w_i_d_e tuning range) we are unable to imagine any advantage for Pb-salts except "legacy" operating hardware.
Pb-salt lasers were until recently available from Laser Components GmbH in Germany. They have sales offices in USA and UK as well. Additionally Muetek IR Laser Systems GmbH in Germany offers variable temperature cryostats suitable for the operation of Pb-salt lasers.
Questions? Comments? Suggestions? Send email to the Webmaster at Boston Electronics.