Efficient Single-Mode GaAs/AlGaAs W Waveguide Phase Modulator with a Low Propagation Loss

Gallium arsenide optical phased array photonic integrated circuit

A 16-channel optical phased array is fabricated on a gallium arsenide photonic integrated circuit platform with a low-complexity process. Tested with a 1064 nm external laser, the array demonstrates 0.92° beamwidth, 15.3° grating-lobe-free steering range, and 12 dB sidelobe level. Based on a reverse biased p-i-n structure, component phase modulators are 3 mm long with DC power consumption of less than 5 µW and greater than 770 MHz electro-optical bandwidth. Separately fabricated 4-mm-long phase modulators based on the same structure demonstrate single-sided Vπ·L modulation efficiency ranging from 0.5 V·cm to 1.22 V·cm when tested at wavelengths from 980 nm to 1360 nm.

Method for in-depth characterization of electro-optic phase modulators

A flexible method to measure the modulation efficiency and residual amplitude modulation, including non-linearities, of phase modulators is presented. The method is based on demodulation of the modulated optical field in the optical domain by means of a heterodyne interferometer and subsequent analysis of the I&Q quadrature components of the corresponding RF beat note signal. As an example, we determine the phase modulation efficiency and residual amplitude modulation for both the TE and TM modes of a GaAs chip-based phase modulator at the wavelength of 1064 nm. From the results of these measurements, we estimate the linear and quadratic electro-optic coefficients for a P-p-n-N GaAs/AlGaAs double heterostructure.

Stable two-wavelength lasers by use of a double alpha-type fiber cavity with fiber grating mirrors

For high-frequency (20-200 GHz) modulated light sources, we developed and investigated two-wavelength lasers using the double alpha-type fiber cavities with fiber grating mirrors. For variations of polarization states and pump powers, parallel alpha-type coupled cavity lasers were found to be more stable than serial lasers.