Dual-channel optical phase measurement system for improved precision.

Developments and applications of a dual-channel phase measurement system are being proposed and experimentally studied by utilizing an optical homodyne technique. In this measurement system, the phase modulation was adopted by using a near-stable Zn-indiffused lithium niobate phase modulator. The proposed method was successfully applied on the simultaneous measurements of the phase-retardation difference between a transmitted light and a reflected light after passing through a nonpolarization beam splitter. The measured stability of the phase-retardation difference was approximately 0.0013 rad.

An optical homodyne technique to measure photorefractive-induced phase drifts in lithium niobate phase modulators.

In this paper, we develop an optical measurement system with capabilities of phase unwrapping, real-time and long-term monitoring for measuring a phase drift caused by photorefractive effects in lithium niobate phase modulators. To extract the phase-drift variations, the measurement setup uses a homodyne interferometer with a phase modulation and a Fast Fourier Transform (FFT) demodulation scheme. The phase-drift characteristics of a traditional Ti-indiffused and a Zn-indiffused phase modulator have been investigated under different applied voltages and throughput powers. These experiments were conducted as a proof-of-concept to demonstrate that the apparatus worked successfully to measure the phase drift of a device in the presence of photorefractive effects. The results indicate that the Zn-indiffused phase modulators have better photorefractive stability than the Ti-indiffused phase modulators.

A novel Zn-indiffused mode converter in x-cut lithium niobate.

A novel Zn-indiffused mode converter has been proposed and experimentally studied in an x-cut/z-propagation lithium niobate at a wavelength of 0.632 mum for the first time. The optimized phase-matching and mode-conversion voltages for maximum conversion are 12 V and -?5 V, respectively. The results show that the proposed mode converter can operate with a stable conversion efficiency of about 99.5% between TM and TE polarizations at a throughput power of 25 muW in a period of 60 min. Moreover, a comparison of optical power-handling stability between the Ti-indiffused and the Zn-indiffused channel waveguides, was explored. The encouraging results indicate that the Zn-indiffused waveguide has better power stability than the Ti-indiffused waveguide. Thus, it is expected that the proposed mode converter will have better stability than the conventional Ti-indiffused ones, especially in the visible wavelength region.