Multiple application segments from data transmission to sensing drive the demand for high-performance photonic integrated circuits. We review advancements in silicon photonics manufacturing platform for datacom and multi-Tb/s optical interconnects.
We report on the first monolithic 1310 nm Vertical Cavity Surface Emitting Lasers (VCSELs) with top and bottom InGaAsP/InP distributed Bragg reflectors (DBRs). The lasers show single mode powers over 1.0 mW at room temperature and single mode powers up to 0.5 mW at 85oC. The lasers, designed to be single mode, have side mode suppression ratios exceeding 45 dB over all temperatures and all powers.
Plasma luminescence spectroscopy was used for precise ablation of bone tissue without damaging nearby soft tissue using an ultrashort pulse laser. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so bone tissue is selectively ablated while preserving the spinal cord.
Temperature and shock wave propagation in water (as a model of tissue) irradiated by sub-picosecond and nanosecond pulses were modeled. The high temperature and pressure generated during sub-picosecond irradiation did not penetrate deeply into the water due to quickly ejected plasma while significant pressure and temperature increases were observed in deep regions with nanosecond pulses. Knowing that the sub- picosecond pulses are effective for tissue ablation, additional studies were done to examine the effect of short pulse widths (less than 20 ps). Ablation threshold, temperature rise and ablation crater quality on human dentine were investigated for different pulse widths in the range of 150 fs - 20 ps. The ablation threshold fluence was approximately 4 times higher with 20 ps pulses than with 150 fs pulses but the quality of the alation craters were not significantly different in this pulse width range.
The plasma mirror is a self-induced, plasma-based optical element which can be inserted into existing experiments to reduce prepulse energy without significant degradation of ultrashort pulse laser light. We have directly observed the nonlinear reflectivity of the plasma mirror as well as the spatial and temporal characteristics of the reflected pulse. The initial measurements indicate that the incident pulse reflects specularly from a high density, highly reflective plasma. The reflected pulse has a smoothed spatial profile and reduced pulsewidth. We outline future work to characterize both the plasma mirror technique of prepulse suppression and its reflected pulse.
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