Katsuaki Magari

1.55 mu m polarization-insensitive high-gain tensile-strained-barrier MQW optical amplifier

A polarization-insensitive semiconductor optical amplifier was realized at a wavelength of 1.55 mu m. The active layer consisted of a tensile-strained-barrier multiple quantum well (MQW) structure. At a driving current of 150 mA, no dependence of the saturation characteristics on modes was obtained. The saturation output power at which the gain decreases 3 dB is 13.3 dBm. A slightly higher saturation output power of 14 dBm was measured at a driving current of 200 mA. No large difference was observed between transverse-electric (TE) and transverse-magnetic (TM) modes. A high gain of 27.5 dB at a polarization sensitivity of 0.5 dB and a high saturation output of 14 dBm were realized simultaneously by using a longer device with reduced residual facet reflectivities.<<ETX>>

Efficient 3-μm difference frequency generation using direct-bonded quasi-phase-matched LiNbO3 ridge waveguides

We fabricate 50-mm-long direct-bonded quasi-phase-matched LiNbO3 ridge waveguides for difference frequency generation in the 3-μm wavelength range. Conversion efficiency of 40%/W is achieved using a 1-μm-band pump and a 1.55-μm-band signal, and a 0.26-mW output is obtained. We also use the device to demonstrate methane gas detection at around 3.3μm.

Polarization insensitive traveling wave type amplifier using strained multiple quantum well structure

Signal gain agreement between TE and TM modes is realized under a specific operation condition in a traveling wave type amplifier using a strained multiple quantum well structure for the first time. The signal gain of the TM mode completely agrees with that of the TE mode at an amplifier driving current of 70 mA. The identical signal gain is 7.5 dB at present. However, the signal gain could be easily improved by using a device with a longer active region. In order to achieve polarization insensitive TWAs, the design parameter is the only confinement factor for the conventional bulk type.<<ETX>>

Optical narrow-band filters using optical amplification with distributed feedback

The amplification characteristics of the distributed-feedback (DFB) laser amplifier are studied. The amplifier has a narrow, single-frequency gain-bandwidth product and the maximum-gain frequency tunability. With these advantages, the amplifier can be applied as an optical narrowband filter. This filter has optical frequency selectivity with an extinction ratio of better than -15 dB for optical inputs separated by 9.8 GHz having different optical input powers. By using a multielectrode DFB laser amplifier, the wide-range tunability of a gain maximum frequency (33.3 GHz) can be obtained while maintaining a constant gain and a constant gain-bandwidth product. Optical frequency selection with an extinction ratio of better then -20 dB can be obtained for two optical inputs separated by 15.4 GHz and having the same input power. >

Tunable optical-wavelength conversion using an optically-triggerable multielectrode distributed feedback laser diode

Tunable optical-wavelength conversion with tunability greater than 5 AA using a multielectrode distributed-feedback laser diode (DFB LD) with a saturable absorber is discussed. This device is not dependent on input polarization and can operate at up to 500 MHz. Preliminary results of an optical switching experiment using the tunable wavelength converter and optical narrowband filter with a DFB LD amplifier are also reported. >

160-Gb/s OTDM transmission using integrated all-optical MUX/DEMUX with all-channel modulation and demultiplexing

This letter provides the first report of 160-Gb/s optical time-division-multiplexed transmission with all-channel independent modulation and all-channel simultaneous demultiplexing. By using a multiplexer and a demultiplexer based on periodically poled lithium niobate and semiconductor optical amplifier hybrid integrated planar lightwave circuits, 160-km transmission is successfully demonstrated.

Polarization-insensitive optical amplifier with tensile-strained-barrier MQW structure

A new approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of a tensile-strained-barrier MQW structure that enhances TM mode gain. Polarization sensitivity below 0.5 dB is realized at a wavelength of 1.56 /spl mu/m. A signal gain of 27.5 dB is obtained along with a saturation output power of 14 dBm. Deriving the refractive indices of well and barrier layers from both experiment and theory, we succeed in separation of the effect of the confinement factor and the gain coefficient. It is determined that TM mode gain enhancement in this structure is primarily due to the increase in the confinement factor. >

Optical frequency‐selective amplification in a distributed feedback type semiconductor laser amplifier

Optical frequency‐selective amplification of an injected optical signal in a distributed feedback type semiconductor laser amplifier is studied. Based on this mechanism an optical demultiplexer with optical gain for optical frequency‐division multiplexing is developed. A 9 GHz spectrum selectivity and a 11 dB extinction ratio are observed.

Widely tunable 3.4 μm band difference frequency generation using apodized χ (2) grating

We achieved apodization in a quasi-phase-matched wavelength converter. The new design yields a large bandwidth and a flat phase-matching response with a high conversion efficiency. Using the method, we demonstrate widely tunable 3.4 μm band difference frequency generation in a LiNbO3 ridge waveguide.

Wide-band polarization-independent tensile-strained InGaAs MQW-SOA gate

A high-performance tensile-strained InGaAs multi-quantum-well semiconductor optical amplifier (MQW-SOA) gate developed for wavelength-division-multiplexing (WDM) applications is reported. The -0.47% InGaAs-strained SOA gate has a very low polarization dependence of 0.3 dB over a driving current between 30 and 60 mA and a wide-input signal wavelength range from 1530 to 1580 nm. The fabrication tolerance of the mesa stripe width is very large, ranging from 1.0 to 1.75 /spl mu/m. The MQW-SOA gate has an extinction ratio of more than 40 dB. The fiber-to-fiber lossless operation current is less than 50 mA over the fiber-amplifier gain band. The gating speed is less than 1 ns.