Tomoyuki Uehara

Optical beat-note frequency stabilization between two lasers using a radio frequency interferometer in the gigahertz frequency band

Abstract. A beat-note frequency stabilization system using a distributed-feedback laser and external cavity laser diode has become a very important technique for laser spectroscopy, where highly stabilized high-frequency beat notes are required. We have developed a simple and versatile system capable of stabilizing the high-frequency beat notes (3 to 11 GHz) of two lasers using a delayed radio frequency self-heterodyne interferometer and have confirmed its basic operation. The frequency stability of the obtained beat notes is higher than 1 MHz in the 3- to 11-GHz frequency range with an average time of 20 s.

Simultaneous photonic generation of two microwave signals with precisely-controllable phase difference using orthogonal polarization modes

Optical microwave or millimeter-wave generation using the beat note of two lightwaves is an attractive technique because of its advantages of frequency-tunable micro/millimeter-wave generation, high selectivity of the operation frequency, and high-speed phase switching of the generated signals owing to the photonics-based scheme. In this paper, we propose and demonstrate the simultaneous generation of two microwave signals with a precisely-controlled phase difference using the orthogonal polarization modes existing in a polarization maintaining fiber. High stability and controllability of the phase difference between the generated two microwave signals was experimentally confirmed.

Frequency stabilization of two orthogonally polarized external cavity laser diodes using a novel γ-type optical configuration consist of a phase modulator and a Faraday rotator mirror

We propose a novel method to stabilize two external cavity lasers for optical generation of microwave and millimeter wave signals. In our method, two 1550-nm, servo-locked external cavity laser diodes (ECLDs) are simultaneously locked to two resonance frequencies of a single Fabry-Perot optical cavity. The stabilization of two lasers are realized by introducing classical FM sideband technique. In .-type optical configuration, two wavelengths from the ECLDs with orthogonal polarization are simultaneously phase modulated by a phase modulator with a Faraday rotator mirror. The .-type optical configuration is designed as a compact, stable and double-pass phase modulation apparatus with same modulation index for two orthogonally polarized signals transmitted through a polarization maintaining fiber. We obtain short-term stability of 200 kHz at an averaging of 10ms, which is measured with the square root of the Allan variance from the beat note between frequency stabilized lasers.

Microwave phase-control scheme based on optical beat wave generation and propagation in an optical fiber

Abstract. A microwave phase-control scheme is proposed and experimentally demonstrated. Two lasers are combined in an optical fiber coupler to generate a beat signal. The beat frequency is tuned by controlling the frequency of one laser. Using the phase shift of the beat waves with different frequencies during the propagation in an optical fiber, the phase of the radio-frequency (RF) signal generated by a photodetector (PD) can be controlled. Using the phase shift during the propagation of beat waves in an optical fiber with different beat frequencies, the phase of the RF signal generated by a PD connected to the fiber can be controlled. A tunable phase shift ranging from 0 deg to 1400 deg is obtained for frequencies from 6 to 10 GHz. This scheme offers the advantages of fast tuning and precise phase control of an RF signal.

Photonic generation of a phase-switchable ASK signal using orthogonal polarization modes of a single optical phase modulator

In this paper, we propose and demonstrate the photonic generation of phase-switchable ASK microwave signal using the orthogonal polarization modes of the optical phase modulator. The two-phase switching operation of the generated microwave signals was experimentally confirmed.

RF-wave generation using external cavity laser diodes frequency-stabilized to single optical cavity by using orthogonal polarized modes

We propose a novel stabilization technique for two 1550-nm band external cavity laser diodes (ECLDs) used in optical generation of microwave and millimeter wave signals. Using FM sideband technique, those two ECLDs are simultaneously locked to two resonant modes of a single Fabry-Perot cavity. In the scheme, a new Υ-type optical configuration is used for simultaneous phase modulation of orthogonally polarized two wavelengths transmitted through slow and fast axis of polarization maintaining fiber. The Υ-type optical configuration, which consists of a phase modulator and a Faraday rotator mirror combined with an optical circulator, is a simple and compact apparatus to achieve double-pass phase modulation with the same modulation index . In this paper, we show the results of frequency stabilization of two ECLDs using Υ-type configuration, and compare with the results obtained in conventional non-Υ-type configuration. Short-term stability of 200 kHz at an averaging of 10 ms is achieved in the simple Υ-type configuration.