Sumitomo Electric Has Developed a DFB-QCL CAN Module, the World's Smallest Mid-infrared CW Light Source for High-Speed Sensing

Sumitomo Electric Industries, Ltd. has developed and begun shipping samples of its compact DFB-QCL (distributed feedback quantum cascade laser)*¹ CAN module, which can oscillate in a single-mode under continuous-wave (CW) condition up to a device temperature of 80℃ in the 7 µm wavelength band. This is the world's smallest CW QCL module, and is expected to find a wide range of applications as a light source for high-speed sensing in industrial, environmental, and medical fields. Two types are available: a temperature-controllable type (15.4 mm in diameter) with built-in thermoelectric cooler (TEC) and an uncooled type (5.6 mm in diameter) without it. With the former, a dedicated mount to drive the module can be also available.

DFB-QCL, which can oscillate in a single mode under CW condition in the 4-20 µm mid-infrared wavelength band, will be used as a compact and high-speed light source for sensing such as high-sensitive and real-time measurements of air polluting, greenhouse, and poisonous gases. It is also applicable for medical diagnoses, such as breath analysis and blood sugar level measurement. However, the power-consumption of the conventional DFB-QCLs had been large, typically more than 5 W, and generated a huge amount of heat during laser operation, and thus they had to be mounted on large and expensive HHL packages*² which provide high heat dissipation.

As a result, drastic downsizing and cost reduction of the module were difficult, which prevented severely the expanding the QCL applications. In addition, difficulty in CW oscillation in high-temperature environments has also restricted this laser's use.

Sumitomo Electric, however, has succeeded in developing a low-power-consumption DFB-QCL module by incorporating our original light-emission structure obtained using the Company's quantum structure design technology. This module realize a stable CW operation using a general-purpose metal can package*³ in the 7 µm wavelength band, which is expected to be used for measuring methane (CH₄), sulfur dioxide (SO₂) hydrogen sulfide (H₂S), and so on.

Features

1. Drastic downsizing is achieved: Compared to conventional HHL modules (32 x 45 x 18 mm), the volume is reduced to be till about 8% (TEC-included type) and about 1% (TEC-less type) of the HHL module.
   • TEC-included type: A TEC and DFB-QCL chip are contained in a 15.4-mm diameter CAN package.
   • TEC-less type: Only a DFB-QCL chip is contained in a 5.6-mm diameter CAN package. Adding an external temperature controller enables the module to produce equivalent characteristics as the TEC-included type.
2. CW and single-mode operation can be obtained up to 80℃ by reducing power-consumption of the QCL device to less than 2 W, and thus substantially reducing heat generation.
3. High optical output sufficient for high-sensitive detection is achieved: more than 30 mW at a device temperature of 20℃ and 10 mW at a device temperature of 60℃ (both typical values). The Company has already succeeded in demonstrating high-sensitive methane detection of up to 1.3 ppb*⁴ with this module.

Sumitomo Electric is also developing other types of DFB-QCLs that oscillate in different wavelength bands, such as the 5 µm band and 8-9 µm band.

The Company plans to exhibit this module at SPIE Photonics West 2018 (January 30 to February 1, 2018 in San Francisco, USA) and at LASER World of PHOTONICS CHINA (March 14 to 16, 2018, in Shanghai, China). At Photonics West 2018, the Company will give an invited talk on the above high-sensitive methane gas sensing.

*1 Distributed feedback quantum cascade laser (DFB-QCL):
A semiconductor laser that enables a single-mode oscillation in the mid-infrared region by incorporating both a built-in wavelength selection structure and a special cascade light-emitting structure.

*2 High Heat Load (HHL) package:
High Heat Load A large box-type package with high heat dissipation, thus used for high power-consumption lasers such as large output-power semiconductor lasers for processing.

*3 metal can package:
An air-tight package consisting of a metal stem with lead pins and a cylinder-shaped cap with an exit window covering the stem. It is less expensive and has a compact size suitable for module-downsizing, and thus it is widely used in low power-consumption semiconductor lasers such as those used for DVDs and optical communications.

*4 Parts per billion (ppb):
A unit that indicates ratio or concentration. 1 ppb = one 10 millionth of 1%.