Recently, Ruichuang Research Institute and Ruichuang Photonics team have made important progress in the research of mid-infrared interband cascade laser (ICL). The team has realized a series of high-performance, room-temperature continuous operation interband cascade lasers with multiple excitation wavelengths, and combined with molecular-beam epitaxy to grow interband cascade laser materials on InAs substrates, and prepared narrow-ridge devices with room-temperature excitation wavelengths close to 4.6 μm. The room temperature excitation wavelengths of the narrow ridge devices are close to 4.6μm and 5.2μm.
It is reported that most interband cascade lasers are grown on GaSb substrates, while the interband cascade lasers reported by Ruichuang's team are grown on InAs substrates, with the waveguide cladding consisting of an InAs/AlSb superlattice and a highly doped InAs layer. Compared to the common GaSb-based interband cascade lasers, the InAs-based interband lasers have lower threshold current densities at longer wavelengths (e.g., longer than 4.5 μm).
(a) Continuous excitation spectra of a device with 4.6 μm wavelength, 2 mm cavity length, and 10 μm ridge width between 20°C and 64°C;
(b) Continuous current-voltage-power curves of the same device between 20°C-64°C
For the interband cascade laser at 4.6 μm wavelength, the room-temperature pulse threshold current density of the broad-ridge device is 292 A/cm2; the narrow-ridge device with a 2-mm cavity length and a 10-μm ridge width has a continuous operating temperature of up to 64 °C and a room-temperature output power of 20 mW; this is the highest continuous operating temperature reported so far at a similar wavelength. For an interband cascade laser at a wavelength of 5.2 μm, the room-temperature pulse threshold current density of the broad-ridge device is 306 A/cm2, while that of the narrow-ridge device with a cavity length of 2 mm and a ridge width of 10 μm reaches the maximum continuous operating temperature of 41 ℃, with a room-temperature output power of 10 mW, where the threshold current density is the lowest reported at similar wavelengths.
The related paper "High-temperature continuous-wave operation of InAs-based interband cascade laser " (DOI: 10.1063/5.0171089) and "InAs-based interband cascade laser operating at 5.17 μm in continuous wave above room temperature" (10.1109/LPT.2023.3335856) published in Applied Physics Letters and IEEE Photonics Technology Letters, respectively.
(a) Continuous excitation spectra of a device with 5.2 μm wavelength, 2 mm cavity length, and 10 μm ridge width between 15 °C and 41 °C;
(b) Continuous current-voltage-power curves of the same device between 15 °C and 41 °C.
The interband cascade laser is based on energy band engineering and quantum mechanics to generate excitation, with high technical content and many development difficulties, which is an important embodiment of the national core technology of nano and quantum devices, and is now listed as an important mid-infrared laser source together with quantum cascade laser (QCL), which has important applications and value in fields such as environmental monitoring, industrial control, medical diagnosis and free-space communication. It has important application value and scientific significance in the fields of environmental monitoring, industrial control, medical diagnosis and free-space communication.
The original concept of interband cascade laser was firstly proposed by Prof. Ruiqing Yang (Rui Q. Yang) of the University of Oklahoma in 1994, and basically the near lattice-matched InAs/GaSb/AlSb three-five material system is used to construct it, and most of the active region is InAs/GaInSb two types of quantum wells, which can cover the wavelength range from mid-infrared to far-infrared. The capability can cover the wavelength range from mid-infrared to far-infrared.
Interband cascade lasers combine the advantages of traditional semiconductor diode lasers and quantum cascade lasers, and have lower threshold power density and threshold current density than quantum cascade lasers that also cover the mid-infrared wavelength range, and this extremely low power consumption advantage is very important in some applications that require portable and battery-powered devices.
At present, the global interband cascade laser market is still dominated by foreign companies, and the domestic market is still in the initial stage of industrial development. The two works reported in this paper signify that Ruichuang Photonics has reached a high technical level in multiple aspects of epitaxial design and device preparation of interband cascade lasers, and has become an enterprise that has mastered the technology of high-performance interband cascade lasers. This work also lays a solid foundation for the development and mass production of single-mode tunable DFB interband cascade lasers.
