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 ( ∼ 14 ∘ at 1 / e 2 ) under maximum output power, and a fast rise time ( <2020
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 ( I th). By combining a low-loss zinc-diffusion aperture with an electroplated copper substrate, we can obtain a highly SM output (side mode suppression ratio > 50 d B ) with a very narrow divergence angle ( 1 / e 2 : ∼ 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 ( I th: 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.
Using the Zn-diffusion and oxide-relief techniques with the optimized aperture sizes, we demonstrate a novel single-mode 940 nm vertical-cavity surface-emitting laser (VCSEL) with high brightness performance. The highly single-mode (SM) output optical spectra (SMSR>50 dB) can be sustained under a full range of bias currents and from room temperature (RT) to 85 • C operation. Under RT operation, the maximum SM power can be as high as 7.1 mW with a moderate threshold current (I th : 1.1mA) and narrow divergence angles in the far-field pattern (FWHM: 5 • , 1/e 2 : 7-8 • ). Furthermore, the maximum 3-dB E-O modulation bandwidth of this high-power SM VCSEL can reach 15 GHz without the lowfrequency roll-off induced by spatial hole burning effect. By using this novel device as the transmitter, we can achieve 25 Gbit/sec error-free (bit-error-ratio (BER) < 1 × 10 −12 ) transmission over a 400 meter OM5 fiber without using any signal processing technique. This novel high-speed and high-brightness SM 940 nm VCSEL can serve as a light source in single-mode fiber for medium-reach (>0.3 km) data communications as well as in free-space optical communication.
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