Journal of Infrared and Millimeter Waves, Volume. 42, Issue 6, 795(2023)
Single mode terahertz quantum cascade lasers based on distributed Bragg reflector
Fig. 1. The schematic diagram of the structure and principle of the DBR laser:(a) the three-dimensional structure of the device,with the absorption boundary,DBR reflector and straight waveguide gain region from left to right in the x-direction,and the terahertz wave emitting from the right cavity surface,the electromagnetic field is resonant in the straight waveguide region,with reflections provided by the DBR and the cavity surface on both sides,respectively,(b) the x-z cross section of the device with a grating period of Λ,an air slit width of Ws,and a thickness of the active region of tAR,and a length of the straight waveguide region of LSR,(c) the schematic diagram of the device,the black line is the reflectivity spectrum of the DBR RDBR(f),and the blue region represents the effective gain spectrum geff(f) of the active region
Fig. 2. The finite element simulation results of the DBR structure with a period Λ of 16.6 μm and a slit width Ws of 3 μm:(a) the photon energy band diagram of the DBR structure,the gray area represents the first forbidden region,and the horizontal axis k represents the wave vector,(b) the reflectivity spectrum of the DBR structure with 30 periods,(c) the reflectivity spectrum of the FP cavity surface,(d) the electric field (|Ez| component) distribution of the incident wave inside the DBR grating when the incident frequency is 2.2 THz and 2.6 THz in the DBR structure
Fig. 3. The experimental flow as well as the resultant diagram:(a) the schematic diagram of the cross-sectional structure of the material after bonding and thinning,(b) the specific process flow diagram of the prepared DBR laser,(c) the SEM diagram of the DBR laser,and the inset is an enlarged view of the DBR reflector area
Fig. 4. The power-current-voltage test plots of FP cavity as well as DBR laser:(a) the power-current-voltage test plots for the FP cavity device of the L970 material bimetallic waveguide,(b)-(d) the power-current-voltage test plots of the DBR laser with periods Λ of 18.6 μm,16.6 μm,and 16 μm,respectively,with the black dots representing the spectral current positions in the lower plots
Fig. 5. Results of the spectral tests of the laser:(a) the spectrum of the FP cavity of material L970,(b) a rough fit of the material gain curve based on the spectral range in (a) and the available paper data,and the dashed line represents the loss of the FP cavity,(c) the spectrum of the device with DBR period Λ of 18.6 μm and slit width Ws of 5 μm. The dotted line is the reflection spectrum of the corresponding parameter DBR,and the blue region is the gain range marked according to (a),(d) and (e) also show the spectra of the two devices and the reflectance spectra of the corresponding DBR with periods Λ of 16.6 μm and 16 μm,respectively,and slit widths Ws of 3 μm and 4 μm,respectively,the inset in (e) is the logarithmic axis spectrum
Fig. 6. The schematic diagram of the THz-DBR-QCL structure with two DBR mirrors on both sides
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Hong-Zhou BAI, Shan-Zhi ZANG, Cheng TAN, Kai WANG, Lianghua GAN, Gang-Yi XU. Single mode terahertz quantum cascade lasers based on distributed Bragg reflector[J]. Journal of Infrared and Millimeter Waves, 2023, 42(6): 795
Category: Research Articles
Received: Mar. 12, 2023
Accepted: --
Published Online: Dec. 26, 2023
The Author Email: Gang-Yi XU (gangyi.xu@mail.sitp.ac.cn)