Kazuo Yamane

All optical mode locking of Fabry–Perot laser diode via mutual injection locking between two longitudinal modes

A method to mode lock a Fabry–Perot laser diode (F–P LD) by purely optical means is proposed. Two F–P modes are mutually injection locked with the aid of injected cw light at the center frequency of the two modes. The other F–P modes are cascadingly mode locked owing to the cavity-enhanced nondegenerate four-wave mixing in the F–P LD. The principle of the method was confirmed by observing the linewidth narrowing of the lasing longitudinal modes and the generated optical pulse train at the repetition frequency of one F–P mode spacing.

Squeezed Vacuum Generation Using Symmetric Nonlinear Polarization Interferometer

Squeezed vacuum generation is demonstrated using an ultrashort pulse fiber laser and a symmetric nonlinear polarization interferometer (NOPI). In this system, the squeezed vacuum can be generated only by passing the ultrashort pulse along the optical fiber. Noise reduction of -1.7 dB below shot noise level is observed. Considering the effect of quantum efficiency in this system, the corresponding magnitude of squeezing is estimated to be -2.7 dB. The system is constructed with all fiber devices and is compact, stable, and useful for practical applications.

Nonlinear Polarization Interferometer for Photon-Number Squeezed Light Generation

We propose a new scheme of photon-number squeezed light generation using a nonlinear polarization interferometer which is constructed by the cascade connection of two polarization-maintaining fibers. Since it is possible to generate photon-number squeezed light by only passing an optical pulse through an optical fiber without spatial alignment, it is expected that the squeezed light can easily and stably be generated in this scheme. The magnitude of maximum squeezing in the numerical analysis is estimated to be about -13 dB. Since the arbitrary dividing ratio and two outputs can be obtained by merely turning the half-wave plates on the input and output side, photon-number squeezed light can be generated for the broad input and output power ranges.

Effect of Group-Velocity Dispersion on Photon-Number Squeezing of Optical Pulses using Optical Fibers and Spectral Filter

Photon-number squeezing of optical pulses using optical fibers and band-pass spectral filters is numerically analyzed. The evolution of the quantum noise in the optical pulse propagation is calculated in both the spectral and time domains. The mechanism of filtering squeezing and the role of the group-velocity dispersion are investigated. It is shown that the squeezing is realized owing to the interaction between the self-phase modulation and the group-velocity dispersion.

Analysis of Generation Mechanism of Photon-Number Squeezed Light Using Ultrashort Pulse and Asymmetric Fiber Loop Mirror

We analyze numerically the generation of photon-number squeezed light using an asymmetric fiber loop mirror. For photon-number squeezed light generation, the maximum squeezing can be obtained using this method. The evolution of the quantum noise for the optical pulse spectra is calculated using the quantized nonlinear Schrodinger equation and linearization approximation. It is shown that the squeezed light is generated by removing the increased quantum noise part of the spectrum and enhancing the decreased quantum noise part of the spectrum, by the interference of two pulses at the beam splitter. Although the mechanism of squeezing is similar to that of a spectral filter, the maximum squeezing is as large as -13 dB due to the interference.

Characteristics of Intensity Noise Reduction of Optical Pulses Using Variable Spectral Filters and Optical Fibers

Noise reduction of optical pulses using variable spectral filters and optical fibers in the anomalous dispersion region is investigated numerically and experimentally. In the numerical analysis, quantum noise evolution of the optical pulse is calculated using a quantized nonlinear Schrodinger equation and linearization approximation. It is shown that when the optical spectrum is in the broadening process, photon-number squeezing can be obtained using a band-pass filter. On the other hand, when the optical spectrum is in the narrowing process, a correlated pulse pair is generated using a band-rejection filter and photon number squeezing can be also observed. In the experiment, the characteristics of noise reduction of optical pulses are investigated using a passively mode-locked fiber laser at 1.55 µm and a variable spectral filter. Noise distribution of optical pulses changes periodically as the fiber input power is changed. Intensity noise of the fiber laser is reduced by as much as 23 dB using the band-pass filter and is slightly reduced below the shot noise level. Using the band-rejection filter, the noise reduction by the correlated pulse pair is confirmed. The characteristics of the experimental results are almost in agreement with those of the numerical ones.

Generation and Detection of Squeezed Light with Phase Tunable Fiber Loop Mirror using Polarization Beam Splitter

Squeezed light generation is demonstrated using a new scheme of nonlinear fiber loop mirror. The squeezed light can be generated stably in a compact setup and the phase difference can be changed arbitrarily. Using a 100 ps mode-locked pulse laser at 1.064 µm and 0.85 µm single-mode fiber, the quantum noise reduction of 2.0 dB below the shot noise level is observed in the frequency range of 25–35 MHz. Accounting for the detection efficiency, this corresponds to 2.9 dB squeezing.

Generation of Squeezed Vacuum using Spectral Filter by Spatial Light Modulator and Nonlinear Polarization Interferometer

We have demonstrated squeezed vacuum generation using an optical fiber, spectral filter consisting of the spatial light modulator (SLM), and a nonlinear polarization interferometer (NOPI). In the SLM filter, we can suppress the classical amplitude noise and modulate the amplitude and phase of incident pulses simultaneously. The NOPI is the easy and stable squeezed light generator. When the incident pulse is optimized using a feedback algorithm, the maximum noise reduction of -2.0 dB is observed and the corresponding magnitude of squeezing is -3.2 dB. The effects of the SLM filter such as classical amplitude noise reduction and phase optimization are confirmed.

Analysis of photon-number squeezed light generation using nonlinear polarization interferometer

We propose new scheme of photon-number squeezed light generation using nonlinear polarization interferometer, in which photon-number squeezed light can be generated only passing through optical fiber. Maximum squeezing is estimated to be about -13 dB.