Alpes Lasers flagship product, the Continuous Wave, Distributed Feedback Grating Quantum Cascade Laser has been the most versatile mid-IR light source since 2005. These lasers are able to emit a single wavelength at a time.
They can be tuned within a range that can reach up to 4 cm-1 ; there exists a variety of modulation schemes which can be used for different purposes. These lasers are available as chips-on-submount or packaged in HHL or TO3 housing.
Key Features
• Continuous Wave
• Single-Mode Spectrum
• Tunable source
• Low Dissipation
• High Beam Quality
• Narrow Linewidth
Key Applications
• Gas Spectroscopy
• Photoacoustic Sensing
• Metrology
HHL package suitable for higher dissipation CW-DFB
TO3 package suitable for lower dissipation CW-DFB
This sample power spectrum density of a 2216.6 cm - 1 CW-DFB-QCL (measured with a N2O reference gas cell) allows to extract the FWHM linewidth (from the blue area) of 2.01MHz over 1s integration time. The dashed black line is the beta-separation line which corresponds to the upper integration limit for the linewidth determination.
Quantum Cascade Lasers are mid-Infrared light sources which can cover a broad range of wavelengths. In a Distributed Feedback Grating (DFB) device, a grating is etched into the active region of the laser and forces the emission to occur at a very specific wavelength which is determined by the grating periodicity.
For this reason, DFB lasers are also known as Single Mode Lasers. The exact wavelength can be adjusted over a small Tuning Range by changing the operating current and/or the temperature of operation; the exact wavelengths available from a given laser will be specified in an individual datasheet.
Specifications
PARAMETER NAME
|
MINIMUM VALUE
|
VALUE TYPICAL
|
MAXIMUM VALUE
|
UNIT
|
NOTE
|
Central
Wavelength
|
4.25
|
|
12.5
|
μm
|
Each laser is specified with a single wavelength or a small range within the available range.
|
Central Frequency
|
800
|
|
2350
|
cm-1
|
|
Operating
Temperature
|
-20
|
20
|
50
|
°C
|
Potential values, only temperatures listed in datasheet are reachable. For lasers in a LLH, HHL or TO3 housing, the chip operation temperature is guaranteed to be reachable with the housing at room temperature (+20°C). For lasers delivered as CoC a method of temperature control is required to operate the laser.
|
Beam Divergence
(Vertical)
|
40
|
60
|
80
|
°
|
The beam diffracts strongly at the output facet of a chip-on-submount. Collimated beam output is possible with a proper packaging; see housing
brochure for details.
|
Beam Divergence
(Horizontal)
|
30
|
40
|
60
|
°
|
|
Linewidth
|
1
|
1
|
30
|
MHz
|
In theory the instantaneous linewidth of a QCL can be extremely low, of the order of kHz. In practice however, the total noise of a system will almost always be given by the noise of the current driver and/or the temperature noise, and when that noise is much higher than the intrinsic noise you can consider the QCL as a perfect transducer and compute the effective amplitude or spectral noise from the datasheet. For typical commercial drivers the effective noise is on the order of MHz.
|
Output Power
|
2
|
20
|
200
|
mW
|
|
Tuning Range
|
0.5
|
1
|
4
|
cm-1
|
Lasers tune with the operation temperature and current, tuning range availability depends on the central wavelength. A minimum tuning range can be specified.
|
Tuning Rate
|
0.05
|
0.1
|
0.2
|
%
|
As a percentage of the central wavelength
|
Storage
Temperature
|
15
|
20
|
65
|
°C
|
Must be kept above the dew point at all times.
|
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