This study conducts comprehensive performance analyses of a commercial photonic-crystal surface-emitting laser (PCSEL) via small-signal measurement and the bit-error-rate test. Meanwhile, the radio frequency characteristics of the PCSEL are unveiled for the first time. Compared to the vertical-cavity surface-emitting lasers, the PCSEL shows great potential for a broader optical bandwidth that is benefited from the high optical-confinement factor. A maximum bandwidth of around 2.32 GHz is experimentally observed when the PCSEL was biased at 340 mA. Moreover, a theoretical calculation was applied to shed light on the characteristics of the small-signal measurement, providing a deep insight into the corresponding intrinsic response model. The signal transmission capability of the PCSEL was investigated as well. The maximum bit rate and corresponding rise time transmitted at 500 Mbps are 1.2 Gbps and 186.16 ps, respectively. Thus, a high-speed PCSEL can be realised with a shrunk form factor, serving as a promising candidate for the next-generation light sources in high-speed optical communication.

By enhancing the differential gain and reducing the capacitance of the 850-nm multi-mode vertical cavity surface emitting laser (VCSEL) with an analog bandwidth beyond 25 GHz via the use of InGaAs/AlGaAs quantum wells and multiple oxide confinement layers, the transmission of directly encoded 4-level pulse amplitude modulation (PAM-4) data at 42 GBaud and 16-quadrature amplitude modulation orthogonal frequency division multiplexing (16-QAM OFDM) data at 35 GBaud are demonstrated. After passing through 100-m OM5 multimode fiber (MMF), the detailed comparison between the VCSELs designed with different aperture sizes of 5.5/7.5 μm is performed. The 7.5-μm-aperture VCSEL provides the higher power with larger quantum efficiency but exhibits the narrower 3-dB bandwidth and higher noise level than those of the 5.5-μm-aperture VCSEL. Shrinking the oxide-confined aperture to 5.5 μm assists the VCSEL to expand its 3-dB bandwidth to 25.2 GHz and suppresses its relative intensity noise to -135 dBc/Hz, which contributes to support the highest data rate up to 84 and 140 Gbit/s, respectively, for PAM-4 and 16-QAM OFDM data under forward error correction criterion at optical back-to-back condition. Even after transmitting through 100-m-long OM5-MMF, the allowable data transmission rate still remains at 80 Gbit/s for PAM-4 and 120 Gbit/s for 16-QAM OFDM with their receiving power penalty of 3.24 and 3.1 dB, respectively, when the data is carried by the 5.5-μm-aperture VCSEL. Such a newly designed VCSEL structure promotes its allowable bandwidth to manifest the feasibility toward 50-GBaud per channel capacity for future data center applications.

This paper attempts to describe a laser diode driver circuit using the depletion mode gallium nitride high electron mobility transistor (D-mode GaN HEMT) to generate nanosecond pulses at a repetition rate up to 10 MHz from the vertical-cavity surface-emitting laser (VCSEL). The feature of this driver circuit is a large instantaneous laser power output designed in the most efficient way. The design specifications include a pulse duration between 10 ns and 100 ns and a peak power up to above 100 W. The pulsed laser diode driver uses the D-mode GaN HEMT, which has very small C_oss difference between turn-on and turn-off states. The analysis is according to a laser diode model that is adjusted to match the VCSEL, made in National Yang Ming Chiao Tung University (NYCU). A design guide is summarized from the derivations and analysis of the proposed laser diode driver. According to the design guide, we selected the capacitor, resistor, and diode components to achieve 10 ns to 100 ns pulse duration for laser lighting. The experiment demonstrated that the maximum power-to-light efficiency can be as high as 86% and the maximum peak power can be 150 W, which matches the specifications of certain applications such as light detection and ranging (LiDAR).

This article describes an optimized design and process for the improvement of the electrical properties of vertical-cavity surface-emitting lasers (VCSELs) via the impurity-induced disordering (IID) technology. Through the IID process, the electrical current path can be tailored to detour around the defect centers introduced by the oxidation process, resulting in a noticeable improvement in the dc and the RF characteristics of the IID VCSEL. The threshold current was reduced from 0.341 to 0.225 mA due to better current injection efficiency in the IID VCSEL. The characteristic temperature of the IID VCSEL increased from 106 to 150 K, and the slope of the I-V characteristics under low-level-injection regime could be improved to a factor of exp(qV/1.2 kT). The RF characteristics also echoed the dc characteristics, which the optical bandwidth of the IID VCSEL enhanced from 18.95 to 23.49 GHz, and showed a prominent difference on the K factor (~0.26 to ~0.22 ns) and the D factor (~7 to ~11 GHz/(mA)1/2). The IID VCSEL is then employed for a data transmission link, an eye diagram was characterized at up to 44 Gb/s and passed 40-Gb/s error-free testing under on-off-keying (OOK) modulation.

In this work, the architecture of a high-power InAlGaP/InGaP vertical-cavity surface-emitting laser (VCSEL) with an emission wavelength of 680 nm was studied. The design of quantum well, including the well thickness, indium composition, and barrier aluminum composition targeting the emission wavelength, was elaborately optimized. Moreover, the influences of leakage current, temperature dependence of optical gain, and resonance mode gain to threshold current under different barrier aluminum compositions were investigated. Lastly, the temperature characteristics of InAlGaP/InGaP VCSEL with substrate removal have also been calculated with 24% and 40.6% improvement in thermal resistance and operating current range, respectively. It holds great promise for high-power red VCSEL application.

In this study, a paradigm for modulating the light emission performance of photonic-crystal surface-emitting laser (PCSEL) via GaN high electron mobility transistor (HEMT) driving circuit is proposed for the first time. For light detection and ranging (LiDAR) system, a faster pulse repetition frequency with shorter pulse width can provide not only high resolution but also sufficiently precise range resolution. Hereupon, comprehensive analyses for such an integrated system are conducted with not only electro-optical responses but also the corresponding optical behaviors. The relevant electrical characteristics of the employed GaN HEMT are examined at first. Next, the integrated system on a matrix board with its corresponding circuit topology is discussed, illustrating the relevant operating principles. Thereby, sufficient systematical scrutinization for relevant light emissions is performed for both photodiode responses and the optical behaviors under different conditions, paving a holistic panorama for the LiDAR system. Thus, prospects for the next generation LiDAR system in high-power and high-speed operation can be expected.