In this work, we demonstrate a novel high-power vertical-cavity surface-emitting laser (VCSEL) array with highly single-mode (SM) and single-polarized output performance without significantly increasing the intra-cavity loss and threshold current (Ith). By combining a low-loss zinc-diffusion aperture with an electroplated copper substrate, we can obtain a highly SM output (side mode suppression ratio >50dB) with a very narrow divergence angle (1/e2:∼10∘) under high output power (3.1 W; 1% duty cycle) and sustain a single polarization state, with a polarization suppression ratio of around 9 dB, under the full range of bias currents. Compared to the reference device without the copper substrate, the demonstrated array can not only switch the output optical spectra from quasi-SM to highly SM but also maintain a close threshold current value (Ith: 0.8 versus 0.7 mA per unit device) and slope efficiency. The enhancement in fundamental mode selectivity of our VCSEL structure can be attributed to the single-polarized lasing mode induced by tensile strain, which is caused by the electroplated copper substrate, as verified by the double-crystal x-ray measurement results.

High-power and single-mode VCSEL arrays with single-polarized outputs by using package-induced tensile strain

We optimized the p-side emission device configuration of photonic-crystal surface-emitting laser (PCSEL) to facilitate the easier chip process and wafer level testing as well as the feasibility of lasing at shorter wavelength. Typically, in order to obtain uniformly distributed current for larger emission area of PCSELs, laser output is designed through the n-side window due to the low hole mobility and thin p-side cladding layer. However, the substrate as well as the epi-layers have to be isolated before the test of each single die on the wafer, which compromised the advantage of wafer-level test of surface emitters. On the other hand, for lasers with emission photon energy higher than the bandgap energy of GaAs substrate, the power will be entirely attenuated. In this study, the optimized p-side emission by applying the transparent conduction layer on top of the p side contact layer to enhance the current distribution and breaking the symmetry of conventional circle pattern in a unit cell to boost the output efficiency is investigated. Through this approach, a high efficiency p-side up PCSEL platform with lower fabrication cost is developed, which is also applicable for short wavelength PCSELs.

Improvement of output efficiency of p-face up photonic-crystal surface-emitting lasers.

We study a metal organic chemical vapor deposition regrowth process for electrically driven photonic-crystal surface-emitting lasers (PCSELs). The photonic-crystal (PC) structure consisting of air ...

Study of an Epitaxial Regrowth Process by MOCVD for Photonic-Crystal Surface-Emitting Lasers

19-element vertical cavity surface emitting laser arrays with inter-vertical cavity surface emitting laser ridge connectors

High-performance two-stage bipolar cascade 905nm vertical cavity surface emitting lasers (VCSELs) are designed and fabricated. Three different designs are investigated to compare the electrical and optical properties. Experimental results show that the current spreading and thermal problems are important factors affecting the device performance. The device with two oxide apertures accompanied with a $1.5\lambda $ -long active region spacing exhibits a very high slope efficiency of 2.27W/A and a relatively high power conversion efficiency of 52.4%. Such high-performance bipolar cascade VCSELs with 905nm are very important for LiDAR and automotive applications.

High Slope Efficiency Bipolar Cascade 905nm Vertical Cavity Surface Emitting Laser

High-power vertical-cavity surface-emitting laser (VCSEL) arrays, which can serve as the light source in modern lidar and three-dimensional optical sensing systems, have recently attracted a lot of attention. In these types of systems, the time-of-flight (ToF) technique, based on the round-trip time of short optical pulses is usually adopted. Further enhancement of the ranging distance and depth resolution in these ToF driven systems by the incorporation of a VCSEL array with a high available power, high brightness (narrow divergence angle), and fast response time is highly desirable. However, a large number of light emission apertures (several hundreds) in the VCSEL array is usually necessary to raise the output power level to several watts. This leads to a large parasitic capacitance and the RC-limited bandwidth may become the dominant limiting factor of the speed of the high-power VCSEL array. In this work, Zn-diffusion and oxide-relief apertures are used to manipulate the optical modes and reduce the parasitic capacitance, respectively, in a unit device for a 940 nm VCSEL array. The demonstrated VCSEL array has a quasi-single-mode output, high available power (4 W; 1% duty cycle), narrow divergence angle (${\sim}{14}^\circ $∼14∘ at ${{1/e}^2}$1/e2) under maximum output power, and a fast rise time ($ {\lt} {100}\;{\rm ps}$<100ps). These results open up new possibilities for further enhancing the performance of ToF sensing systems at the 940 nm wavelength.

Tzong Liang Tsai

Papers

High-brightness and high-speed vertical cavity surface-emitting laser arrays