Changchun Institute of Optics and Mechanics Proposes 8-Channel Complex-Coupled DFB Laser Array for Near-Infrared Gas Sensing

Changchun Institute of Optics, Fine Mechanics and Physics Proposes and Validates a Complex-Coupled Multi-Wavelength Laser Array: A New Integrated Light Source Technology for Near-Infrared Gas Sensing

Published: 2026-05-06

Recently, a team led by Academician Wang Lijun at the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP), Chinese Academy of Sciences, in collaboration with Professor Zheng Chuantao's team at Jilin University, published a research paper in Optics and Laser Technology titled "A Multi-Wavelength Complex-coupled DFB Laser Array Based on High-Order Surface Gratings for Gas Sensing Applications." The corresponding author is Researcher Liang Lei, and the first author is doctoral student Hu Miao.

The study proposes and experimentally demonstrates an 8-channel complex-coupled distributed feedback (DFB) semiconductor laser array based on high-order surface gratings and periodic current injection. Without epitaxial regrowth or nanoscale lithography, it achieves narrow-linewidth, high-power, wavelength-scalable multi-wavelength laser output, offering a low-cost, high-performance light source solution for near-infrared integrated multi-component gas sensing, with important application value in environmental monitoring, integrated photonics and other fields.

In absorption spectroscopy detection of multi-component trace gases, laser sources must simultaneously meet requirements such as narrow linewidth, high output power and multi-wavelength tunability. Conventional multi-wavelength DFB laser arrays often rely on buried Bragg grating structures, which involve complex processes, high manufacturing costs and difficult wavelength consistency control, limiting their use in high-precision, multi-component integrated gas detection systems. To address this, the research team proposed a complex-coupling mechanism combining "high-order surface gratings + periodic current injection." High-order gratings on the ridge waveguide surface provide effective refractive index modulation, while segmented P-type electrodes and SiO₂ insulation trenches achieve periodic gain modulation. The two act synergistically to form complex-coupled feedback, enhancing mode selectivity while simplifying the fabrication process.

Schematic of the structure and operating principle of the 8-channel complex-coupled DFB laser array

Core Technology Highlights

Innovative structural design: Without epitaxial regrowth or nanoscale lithography, a composite structure combining high-order surface gratings with periodic current injection achieves synergistic refractive index and gain modulation, establishing a stable complex-coupled DFB mechanism.

Hole concentration (a)–(f) as a function of etch depth (400–900 nm), with corresponding fitting functions.

Outstanding performance: Under continuous-wave operation at 25°C, the 8-channel laser array covers emission wavelengths of 1508–1583 nm, with stable single-mode output on every channel, a side-mode suppression ratio (SMSR) exceeding 45 dB, and a threshold current of about 100 mA. At a drive current of 700 mA, the maximum single-channel output power reaches 175 mW, with a linewidth of 2.08–3.51 MHz, combining high power with narrow linewidth. Through current and temperature tuning, each channel offers 4–5 nm of continuous wavelength adjustment; for the 1550 nm channel, the current tuning coefficient is 0.007 nm/mA and the temperature tuning coefficient is 0.12 nm/°C, meeting the matching requirements of various gas absorption lines.

(a) Voltage-current (V-I) and optical power-current (P-I) characteristics of an eight-channel distributed feedback (DFB) laser array under continuous-wave (CW) operation at 25°C. (b) Slope efficiency of each channel versus center wavelength.

(a) Center wavelengths of the eight-channel laser array; (b) discrete emission spectra of the eight-channel laser array.

(a) Wavelength versus injection current for the eight-channel DFB laser array; (b) wavelength versus temperature for the eight-channel DFB laser array.

Application validation results

The research team validated the practicality of the laser array using two typical sensing configurations:

For acetylene (C₂H₂) detection, intensity modulation spectroscopy targeting the 1520.1 nm absorption line achieved a detection limit as low as 200 ppm at an optimal averaging time of 46 s, with a response time of just 2.8 s, demonstrating rapid detection capability;

For carbon dioxide (CO₂) detection, a cavity-enhanced absorption spectroscopy (CEAS) configuration targeting the 1577.4 nm absorption line achieved a detection limit of 7.75 ppm at an optimal averaging time of 67.6 s, and 134.9 ppm in a 0.4 s rapid detection mode, balancing detection sensitivity with response speed.

The laser array reduces manufacturing cost through a simplified process, while offering an integrated light source solution for multi-component gas sensing with its combination of wide wavelength coverage, high power and narrow linewidth. The team will next advance on-chain integration of the device, optimize channel expansion and thermal management, support the development of compact spectroscopic sensing modules, and promote large-scale deployment in fields such as environmental monitoring and industrial process control.