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IR Quantum Cascade Lasers (QCL)

QCLs from Alpes Lasers are generally available from inventory in the wavelength region from 3.2 to 16+ microns. Ongoing developments are expanding the waveband ranges to both higher and lower wavelengths.

There are a range of options for packaging your QCL.

Devices are available as:

Individual single-mode lasers. Distributed feedback, or DFB, devices are available in continuous-wave (CW) or pulsed operation.

Standard Fabry-Pérot (FP). FP QCLs do not have an integrated optical grating to select a single spectral mode

High Power multimode sources. These Quantum Cascade Lasers have a minimum average power of 1W and more than 9W of peak power. Available in a collimated HHL package with a dedicated driver, these lasers can be used for free-space optical communications, energy deposition, illumination and IR countermeasures.

Broad Gain lasers. These lasers are Fabry-Pérot lasers designed for maximum width of the gain profile. They can be used as broad spectrum illuminators for spectroscopy or imaging. Combined with an anti-reflection coating, they are suitable for use in an external cavity to obtain a tunable laser with wide tuning range. Their wide and flat gain spectrum can also be suitable to develop frequency combs.

Extended tuning sources available in HHL packages Alpes Lasers offers two types of extended tuning devices, both of which allow rapid tuning at fixed temperature in a wider range than standard DFB lasers. The QC-ET allows fully continuous tuning over 0.4% of the central wavelength, while the QC-XT allows piece-wise continuous tuning over 2% of the central wavelength.

Frequency Comb Quantum Cascade Lasers. Frequency Comb QCL are devices emitting light on a wide spectrum consisting of equidistant peaks in frequency space. The distance between these peaks being fixed, typically given by the pulse repetition rate of a train of ultrashort pulses, they can be used as rulers in the frequency domain for Frequency Comb Spectroscopy.

External Cavity Kit for larger tuning range. Alpes Lasers’ line of External Cavity Laser Kit (ECLK) is designed for single-mode operation with wide spectral tunability. The ECLK consists of a quantum cascade laser (QCL) gain chip, a grating-tuned extended optical cavity in Littrow configuration, laser drive electronics, an Alpes Lasers TC-3 temperature controller, and a graphical user interface software.

SWIR Laser Diodes.  Short Wave Infrared Laser Diodes are continuous wave, multiple longitudinal mode Fabry-Perot devices emitting light over a bandwidth of ~20 nm with output power up to 50 mW. They are offered either as chip-on-carrier or encapsulated in a low power TO-66 package with collimated or divergent free-space beam output.

Alpes SWIR Laser Diodes can be tailored in the range from 1.45-2.2 microns with each design having a bandwidth of ~20 nm. Available wavelengths include the absorption bands of N2O, H2O, CH4 and HCl among others.

Starter kit: we offer a “starter kit” of hardware to stabilize the QCL device temperature at any temp from -30C to +30C and to energize (drive) the device. Details of the “starter kit” are contained in our catalog.

Last, but not least, QCLs are made on wafers. Each wafer can contain many devices of similar performance. 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. If one meets your needs it may be less expensive and faster delivery than an entirely new one.

See our catalog at the link at the bottom of the page.

Linked below are the current inventory of  single mode lasers in stock at Alpes.  These lasers are available upon request with a typical lead time of 2 to 6 weeks for chips on NS carrier and 6 to 8 weeks with an hermetic package.

These lasers are able to emit a single wavelength at a time. They can be tuned within a range that can reach up to 10 cm-1; there exists a variety of modulation schemes which can be used for different purposes. DFB lasers are mostly used for spectroscopy.

QCL are ‘naturally’ multi-wavelength Fabry-Perot (FP-QCL) devices unless some mechanism is applied to have the laser emit at a single frequency/wavelength.

There are two principle ways to achieve single wavelength operation. The first is to ‘write’ a grating on the device itself so that the device emits at a specific wavelength set by the grating frequency. Tuning is then accomplished over a very 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 path length 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 referred to as “distributed feedback” mechanisms or DFBs, and a QCL that has such a grating is a DFB-QCL.

The typical spectral range of these single mode devices is 700 to 24000 wavenumbers (cm-1) or14 down to 4 microns in wavelength.

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”.

For larger tuning ranges we also supply or an External Cavity Laser Kit (ECLK) or you can buy external cavity devices from Block Engineering, Daylight Solutions or Pranalytica.

Frequency Comb QCL are also available. These devices emit light on a wide spectrum consisting of equidistant peaks in frequency space.

 

QCLs are tunable infrared light sources. Our QCLs are from our partners, Alpes Lasers SA in Switzerland. QCL technology and production has rapidly matured, and they are being applied in a wide range of applications including:

  • Security
  • Defense
  • Environmental Monitoring
  • Gas Sensing
  • Life Sciences
  • Scientific Instrumentation

Why QCLs? Because most chemical compounds have their fundamental vibrational modes in the mid-infrared, spanning approximately the wavelength region from 3 to 15μm, this part of the electromagnetic spectrum is very important for gas sensing and spectroscopy applications. Even more important are the two atmospheric windows at 3-5μm and 8-12μm. The transparency of the atmosphere in these two windows allows remote sensing and detection.

New devices are continually available, either expanded wave nember or new device designs and applications.  Of note:

  1. Alpes Lasers can now offer Broad Gain Interband Cascade Laser (ICL) chips for use in External cavity systems. ICL allow emission in at shorter wavelengths than traditional QCL which are particularly interesting for hydrocarbon detection. The initially offered chip covers the range 3.2-3.6 um (2820-3070 cm-1) which contains interesting absorption lines for CH4, C2H6, HCl, CH2O (formaldehyde) in particular.
  2. Frequency Comb Quantum Cascade Lasers emitting light on a wide spectrum consisting of equidistant peaks in frequency space (info).
  3. device are also now available in Terahertz frequencies (1 – 5 THz).  Call for additional information.
  4. SWIR laser diodes (1.5 – 2.2 um) up to 50 mW output (info)

See the QCL Products and catalog below for further information.

Questions to answer about QCLs

  1. Which wavelengths should the laser cover?
  2. Should the laser be tunable?
  3. Will you use wavelength modulation, and of which type?
  4. What is the minimum power needed? Is average or peak power the important criteria?
  5. Should the beam be collimated?
  6. Do you need a housing for the laser (Lab, HHL, TO, sub-mount, etc)?
  7. In what type of environment will the laser be used? For example, is it for laboratory or field use, is water cooling available, etc.
  8. Will you require drivers, or do you plan to use third party drivers?
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