Quantum and Interband Cascade Lasers: Distributed Feedback, HHL Package

Webpage Features
	Clicking this icon opens a window that contains specifications and mechanical drawings.
	Clicking this icon allows you to download our standard support documentation.
Choose Item	Clicking the words "Choose Item" opens a drop-down list containing all of the in-stock lasers around the desired center wavelength. The red icon next to the serial number then allows you to download L-I-V and spectral measurements for that serial-numbered device.

Features

• Single-Wavelength Distributed Feedback Quantum or Interband Cascade Lasers (DFB QCLs and ICLs)
• High Heat Load Package Simplifies Thermal Management and System Integration
• Collimated Laser Emission Through Wedged Window
• Used in Chemical Analysis, Sensing, and IR Countermeasures
• Custom Packages and Wavelengths from 3 to 12 µm Available via Tech Support

The MIR quantum and interband cascade lasers on this webpage are offered in high heat load (HHL) packages with industry-standard pinouts and package dimensions. Each package incorporates a built-in thermistor and thermoelectric cooler (TEC) for active temperature management and prolonged laser lifetime, and also includes an internal aspheric lens that collimates the laser's output.

Distributed feedback QCLs and ICLs emit at a well defined center wavelength, making them popular for applications such as chemical sensing and sample analysis. They provide single transverse mode operation. By tuning the input current and operating temperature, the laser output can be tuned over a narrow range of at least 1 cm^-1. Before shipment, the output spectrum, optical power, and L-I-V curve are measured for each serial-numbered device by an automated test station. These measurements are available below and are also included on a data sheet with the laser.

Our ICLs emit a horizontally polarized beam at wavelengths as long as 4.0 µm, while our QCLs emit a vertically polarized beam at wavelengths as long as 11 µm. ICLs will also typically have lower voltage requirements and threshold currents, thus leading to lower optical output powers. Conversely, QCLs will consume more power and will therefore have higher output powers.

Some of Thorlabs' high heat load DFB quantum and interband cascade lasers are uniquely suited for gas sensing and analysis. Select high heat load QCLs are designed to emit at wavelengths ideal for many gases commonly studied in spectroscopy (see the Spectroscopy tab for more information). These DFB quantum cascade lasers are guaranteed to reach their specified wavelengths within their tuning range and are single wavelength, allowing them to be tuned to specific gas spectra. Thorlabs also sells the ID3250HHLH interband cascade laser, which can be used for methane sensing. A list of these QCLs can be found in the Spectroscopy tab above, and more information is available by clicking on the blue info icons () next to the relevant Item #s below.

Package Details 
As measured from the bottom of the package, the emission height is 12.7 ± 0.13 mm. The output beam is collimated by an AR-coated black diamond aspheric lens and then coupled out of the package through a wedged zinc sulfide (ZnS) window. This wedge prevents back reflections from returning to the laser chip, but also causes the output beam to deviate downward from the normal by either 2.0° ± 1.5° or 2.0° ± 0.75°, as shown in the Drawing tab of the blue info icons () below. Our stocked lasers are sealed, although the seal is not hermetic; hermetically sealed versions are available by contacting Tech Support.

Each laser is electrically isolated from its mount. Heat loads for these lasers can be up to 38 W, so they must be mounted on a thermally conductive surface to prevent heat buildup. Thorlabs' LCM100(/M) liquid-cooled mount is designed specifically to provide additional thermal regulation of the HHL laser package. The CAB4007A and CAB4007B dual laser diode and TEC connector cables are also available to connect an ITC400xQCL series controller to the LCM100(/M) mount or directly to an HHL laser package, respectively. Please note that third-party cables for high heat load packages are typically not rated for the 4.5 A maximum current of the internal thermoelectric cooler. The Handling tab contains more tips and information. These QCLs and ICLs are specified for CW output. While pulsed output is possible, this application prohibits current tuning, and performance is not guaranteed. These lasers do not have built-in monitor photodiodes and therefore cannot be operated in constant power mode.

For OEM applications, Thorlabs also offers QCLs on a compact D-mount package (12.0 mm × 4.5 mm × 2.8 mm).

Click to Enlarge
Available Wavelengths for Custom DFB Lasers

DFB QCLs at Custom Wavelengths

Thorlabs manufactures custom and OEM quantum cascade lasers in high volumes. We maintain a broad chip inventory at our Jessup, Maryland laser manufacturing facility (see the graph to the left), and can deliver DFB lasers with custom center wavelengths that are qualified to a user-defined wavelength precision.

More details are available on the Custom & OEM Lasers tab. To inquire about pricing and availability, please contact us. A semiconductor specialist will contact you within 24 hours or the next business day.

Current and Temperature Controllers

Use the tables below to select a compatible controller for our MIR lasers. The first table lists the controllers with which a particular MIR laser is compatible, and the second table contains selected information on each controller. Complete information on each controller is available in its full web presentation. We particularly recommend our ITC4002QCL and ITC4005QCL controllers, which have high compliance voltages of 17 V and 20 V, respectively. Together, these drivers support the current and voltage requirements of our entire line of Mid-IR Lasers. To get L-I-V and spectral measurements of a specific, serial-numbered device, click "Choose Item" next to the part number below, then click on the Docs Icon next to the serial number of the device.

Laser and Controller Compatibility

• Thorlabs offers the CAB4007A and CAB4007B connector cables for connecting high heat load lasers to the ITC4002QCL or ITC4005QCL controllers. Please note that third-party cables for these packages are typically not rated for the 4.5 A maximum current of the internal thermoelectric cooler.

Controller Selection Guide

Handling High Heat Load Lasers

Proper precautions must be taken when handling and using high heat load lasers. Otherwise, permanent damage to the device will occur. Members of our Technical Support staff are available to discuss possible operation issues.

Avoid Static
Since these lasers are sensitive to electrostatic shock, they should always be handled using standard static avoidance practices.

Avoid Dust and Other Particulates
Contamination of the window must be avoided. Do not blow on the window or expose it to smoke, dust, oils, or adhesive films. The window is particularly sensitive to dust accumulation. During standard operation, dust can burn onto it, which will lead to premature degradation of the laser performance. If operating a high heat load laser for long periods of time outside a cleanroom, it should be sealed in a container to prevent dust accumulation.

Use a Current Source Specifically Designed for Lasers
These lasers should always be used with a high-quality constant current driver specifically designed for use with lasers. Lab-grade power supplies will not provide the low current noise required for stable operation, nor will they prevent current spikes that result in immediate and permanent damage.

Thermally Regulate the Laser
Temperature regulation is required to operate the laser for any amount of time. The temperature regulation apparatus should be rated to dissipate the maximum heat load that can be drawn by the laser. For our high heat load DFB QCLs and ICLs, this value is 38 W.

The bottom face of the high heat load package is machined flat to make proper thermal contact with a heat sink. Ideally, the heat sink will be actively temperature regulated to ensure proper heat conduction. Thorlabs' LCM100(/M) Liquid-Cooled Mount for HHL lasers is capable of disipating up to 140 W of heat at 25 °C making it an ideal choice for temperature-controlled operation of HHL lasers. A fan may also serve to move the heat away from the package and prevent thermal runaway. However, the fan should not blow air on or at the laser itself. Thermal grease, pyrolytic graphite, and water cooling methods may also be employed for temperature regulation.

For assistance in picking a suitable temperature controller for your application, please contact Tech Support.

Carefully Make Electrical Connections
When making electrical connections, care must be taken. The flux fumes created by soldering can cause laser damage, so care must be taken to avoid this.

Although soldering to the leads of our HHL lasers is possible, we generally recommend using cables specifically designed for HHL packages. Thorlabs' CAB4007B LD / TEC cable is specifically designed to connect any standard HHL laser package directly to the ITC400xQCL series of laser diode and TEC controllers. The CAB4007A LD / TEC cable can be used to connect an ITC400xQCL controller directly to the LCM100(/M) mount. Please note that third-party cables for high heat load packages are typically not rated for the 4.5 A maximum current of the internal thermoelectric cooler. If soldering to the leads on an HHL package, the maximum soldering temperature and time are 250 °C and 10 seconds, respectively.

Minimize Physical Handling
As any interaction with the package carries the risk of contamination and damage, any movement of the laser should be planned in advance and carefully carried out. It is important to avoid mechanical shocks. Dropping the laser package from any height can cause the unit to permanently fail.

Gas-Phase Spectroscopy Using Distributed Feedback Lasers

Distributed Feedback Quantum and Interband Cascade Lasers (DFB QCLs and ICLs) offer many attractive features for spectroscopy. They emit at a single wavelength within the mid-IR, where many gaseous species characteristically absorb. Moreover, their emission wavelength is easily tuned (typical tuning range: 1 - 5 cm^-1) by changing the drive current and operating temperature of the laser, making them ideal for isolating narrow gas absorption lines. Finally, quantum cascade lasers offer relatively high output power (typically 40 - 120 mW at rollover current), helping improve measurement sensitivity. ICLs will typically have a low output power, but a far lower power consumption.

The DFB QCLs on this page emit at wavelengths that range from 4.472 to 11.00 µm (2173 cm^-1 to 909 cm^-1), while our DFB ICLs emit at wavelengths that range from 3.00 to 4.00 µm (3333 cm^-1 to 2500 cm^-1). If we do not stock the wavelength required for your application, custom wavelengths are available by contacting Tech Support.

The tuning range of individual DFB QCLs and ICLs depends greatly on the actual laser device. Each DFB QCL or ICL is a unique device with its own threshold current, rollover current, and spectrum. Since the wavelength and power of DFB QCLs and ICLs change over the tuning range, operating the lasers near the rollover current is not always desirable in spectroscopy measurements, which require specific wavelengths. The driving current and operating temperature of DFB QCLs and ICLs can be adjusted to change the output signal to the desired wavelength and power.

An example absorption spectrum of nitric oxide (NO) is shown below on the left. The highlighted blue region, centered on 1900 cm^-1, overlaps with the tuning range of the QD5263HH QCL; tuning data from a sample QD5263HH QCL is shown below to the right for comparison. The QD5263HH QCLs can be precisely tuned to the NO absorption peak at 1900 cm^-1. Click on the blue icons () below for more information on how the emission of each laser in the table above overlaps with the absorption profile of the targeted gas.

DFB QCLs and ICLs are ideal for use in photoacoustic spectroscopy, a technique based on the photoacoustic effect that is able to accurately detect trace gas concentrations for a wide variety of applications. Thorlabs offers an Acoustic Detection Module that can be used with our DFB QCLs and ICLs to build custom QEPAS sensors that target the absorption of a specific gas. We also offer a Quartz-Enhanced Photoacoustic Sensor that targets a methane absorption line to detect trace amounts of methane in a gas.

Click to Enlarge The shaded region overlaps the tuning range of the QD5263HH distributed feedback QCL. See the graph to the right for tuning data from a sample QD5263HH QCL.

Click to Enlarge Tuning data for a sample QD5263HH distributed feedback QCL. See the graph to the left for the absorption peaks of nitric oxide (NO) that can be detected using this laser.