Thermo-optic Phase Modulator Research Articles

Submilliwatt Silicon Nitride Thermo-Optic Modulator Operating at 532 nm

Optical phase control is essential for optical beam steering applications. The silicon nitride thermo-optic modulator generally suffers from high electrical power consumption. Microresonator and multipass structures could reduce the electrical power consumption of silicon nitride thermo-optic modulators, with the drawback of a narrow operating bandwidth and high insertion loss. We demonstrate a single-pass silicon nitride thermo-optic phase modulator at 532 nm with low insertion loss and low power consumption, achieving a π phase shift power consumption down to 0.63 mW in a Mach–Zehnder switch. The rise and fall time are around 1.07 ms and 0.67 ms, respectively.

Temporal response of polymer waveguide beam scanner with thermo-optic phase-modulator array.

Solid-state light detection and ranging, capable of performing beam scanning without using any mechanical moving parts, requires a phase-modulator array. Polymers facilitate the fabrication of efficient phase modulators with low drive power, owing to their high thermo-optic (TO) effect and low thermal conductivity. We designed and fabricated a polymeric phase-modulator array and analyzed the temporal response of the TO phase modulator. The frequency response of the phase modulator was measured for a Mach-Zehnder interferometer (MZI), and the transfer function was modeled in terms of multiple poles and zeros. The frequency response of a fabricated beam-scanning device incorporating the TO phase modulator was also measured. The temporal response of the beam scanner was confirmed to coincide well with that of the MZI modulator. The device exhibited a fast rise time of 12 ms, accompanied by slight power variations appearing for a long period (over hundreds of seconds), which originated from the inherent viscoelastic effect of the polymer materials.

Single-photon interference using silica-based AMZI with phase modulation

An asymmetric Mach-Zehnder interferometer (AMZI) which comprised a variable optical attenuator (VOA), a thermo-optic phase modulator (TOPM) and a delay line of 740 ps was designed and fabricated using silica-based planar lightwave circuit technology. Two identical AMZI chips were connected in series to demonstrate the single photon interference in the middle pulse. The experimental results showed the TOPM can modulate the phase difference between the double pulses. The single photon interference visibility was dependent on the temperature and the polarization of the input light. The observed maximum visibility was 98.38% when the temperature of temperature controller (TEC) was 10 °C. And the interference visibility was dependent on the polarization of the input light. The AMZI could form the basis of the passive decoder in the future quantum cryptography systems.

Optical Voltage Sensors Based on Integrated Optical Polarization-Rotated Reflection Interferometry

Optical voltage sensors based on reflection interferometry of two orthogonal polarizations have been demonstrated by using a polymeric integrated optic device, in which a thermooptic phase modulator, a polarization converter, and a polarizer are integrated on a single chip. The sensing probe for electric field measurement was prepared by assembling an LiTaO3 electrooptic crystal along with a polarization maintaining collimator, a Faraday rotator, and a dielectric mirror. Spectral bandwidth of the light source was optimized to be 16.5 nm in order to provide low noise and good extinction ratio in the reflection interferometry. For an applied voltage of 60 Hz, 4 ${\rm kV}_{\rm pp} $ , the sensor exhibited linear response with a phase retardation sensitivity of 0.5°/ ${\rm kV}$ .

Polymeric Integrated-Optic Bias Chip for Optical Voltage Transducers

The operating bias point of optical voltage transducers (OVTs) must be adjusted to a quadrature phase point through the compensation of residual birefringence induced by the optical fiber and sensor head. An integrated optical device consisting of a polymeric waveguide 3-dB coupler, TE-pass polarizer, thermo-optic phase modulator, and polarization converter was proposed for adjusting the operating bias point. A high-voltage sensor probe was prepared with a LiTaO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> electro-optic crystal sandwiched by Teflon spacers. The operating point control was confirmed by measuring the output polarization change on the Poincaré sphere. Preliminary OVT experiment was performed by applying a high-voltage signal of 60 Hz, 4 kV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> , and the sensor exhibited linear response with a sensitivity of 9.4 mrad/kV.

Reduction of backscattering-inducednoise byternary phase shift keying in resonator micro-opticgyro integrated on silica planar lightwave circuit

The authors propose a method that uses ternary phase shift keying modulation to eliminate backscattering-induced noise in a resonator micro-optic gyro (R-MOG) integrated onto a silica planar lightwave circuit (PLC). Ternary modulation overcomes limitations on the degree of elimination possible caused by the narrow bandwidth of the thermo-optic phase modulator on PLC, the bandwidth of which is limited to 1 kHz.

Polarization stabilizer using a polarization splitter and a thermooptic polymer waveguide device

For the stabilization of the time-varying light polarization in the optical fiber, we demonstrates a polarization stabilizer by using a fiber-optic polarization splitter, a passive polarization converter, and a power equalizing waveguide device. Because the ratio of the output light power from the polarization splitter is time-varying depending on the input polarization, we adopt a power equalizer consisting of a polymeric thermooptic (TO) phase modulator and an asymmetric X-junction waveguide. A feedback signal is obtained from the difference of the two outputs of the power equalizer. Then it is applied to the TO phase modulator. The output power is stabilized with the TE polarization independent of the time-varying polarization state of the input light.

Integrated Q-switched multiple-cavity glass waveguide laser

A novel Q-switching scheme, using rapid variation of the path difference between the cavities of a multiple-cavity resonator, is described. A thermooptic phase modulator was used to switch the cavity loss of a Y-junction glass waveguide laser between high and low states. Q-switched pulses with durations of 5 mu s and peak powers of 70 mW were obtained. >