Novel photonic integrated circuits devices based on AlGaInAs/InP

Sun, Xiao (2024) Novel photonic integrated circuits devices based on AlGaInAs/InP. PhD thesis, University of Glasgow.

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AlGaInAs/InP material system's unique properties, such as a larger conduction band discontinuity (ΔEc = 0.72ΔEg) and a smaller valance band discontinuity have made it an attractive choice for photonic integrated circuits (PIC) devices. In this thesis, several novel PIC devices have been designed, fabricated, and characterized based on conventional 1550 nm AlGaInAs/InP multiple quantum well (MQW) laser diode (LD) epilayer structure.
The first device is the polarization mode converter (PMC), which is monolithically integrated with a sidewall grating (SWG) distributed feedback Bragg (DFB) laser. The study highlights two kinds of PMC with different waveguide structures: the half-ridge waveguide and the stepped-height ridge waveguide. Based on the simulation results, it was observed that the half-ridge waveguide achieved a polarization conversion efficiency (PCE) of approximately 90% with a half-beat length of 1200 μm. In contrast, the stepped-height ridge waveguide demonstrated a significantly superior PCE of 97.3 % with a half-beat length of 490 μm. Subsequently, the stepped-height ridge waveguide PMCs integrated with the SWG DFB laser were fabricated utilizing E-beam lithography and inductively coupled plasma (ICP) etching techniques. The achieved results indicated a PCE of 98.4% over a broad range of DFB injection currents at 1555 nm wavelength and a PCE > 90% over the wavelength range of 1543 to 1568 nm. The second device is the PMC integrated with SWG DFB laser and differential phase shifter (DPS)(100-µm-long) to achieve active polarization control, and a nearly 60° rotation of the Stokes vector on the Poincaré sphere was obtained with a range of DPS bias voltage from 0 V to –3.0 V, which exhibited excellent agreement with the simulation result. 360° rotation of the Stokes vector on the Poincaré sphere is expected by using a 900- µm-long quantum well intermixed (100 nm blueshift) DPS.
The third device presented is the eight-channel electroabsorption modulated lasers (EMLs) array based on sidewall four phase-shifted sampled Bragg gratings(4PS-SBG), a C-band eight-channel EML array is presented, with a channel spacing of 0.8 nm. The use of 4PS-SBG sidewall DFB lasers can preserve high coupling coefficients (0.9 times of continuous uniform gratings) and maintain precise channel spacing control, significantly simplifying the EML device fabrication process, requiring only one metalorganic vapor-phase epitaxy (MOVPE) step and one III-V material etch. The DFB lasers exhibit side mode suppression ratios (SMSRs) greater than 42 dB, while the integrated EAM achieves a 20 dB extinction ratio (ER), and the 3-dB modulation bandwidth is more than 20 GHz.
By the way, I have designed, optimized, and fabricated two innovative InP-based devices: the 1D and 2D topological photonic crystal lasers. However, further optimization of the fabrication processes is required to ensure the functionality of these two devices.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: T Technology > T Technology (General)
T Technology > TA Engineering (General). Civil engineering (General)
T Technology > TK Electrical engineering. Electronics Nuclear engineering
Colleges/Schools: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Supervisor's Name: Hou, Dr Lianping
Date of Award: 2024
Depositing User: Theses Team
Unique ID: glathesis:2024-84180
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 02 Apr 2024 12:52
Last Modified: 02 Apr 2024 12:54
Thesis DOI: 10.5525/gla.thesis.84180
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