Kiyofumi Kikuchi

High-gain, wide-dynamic-range parametric interaction in Mg-doped LiNbO 3 quasi-phase-matched adhered ridge waveguide

With recent developments and optimizations for quasi-phase-matched adhered ridge waveguide (QPM-ARW), outstanding performances containing efficient amplification were demonstrated by difference frequency generation (DFG) and optical parametric amplification (OPA). A maximum channel conversion efficiency of +7.6 dB (570%) was achieved in a telecommunication band using a 50 mm-long device, when coupling with 160 mW pump. Simultaneously, the input signal was amplified up to +9.5 dB (890%).

Parametric Tunable Dispersion Compensation With Spectrally Noninverting Wavelength Conversion Using Quasi-Phase-Matched Adhered Ridge Waveguide

We develop a highly efficient quasi-phase-matched adhered ridge waveguide (QPM-ARW) in LiNbO3 as a nonlinear material, and demonstrate tunable wavelength conversion without spectral inversion (SI) and parametric tunable dispersion compensation for a single-mode fiber (SMF) link. The QPM-ARW module with a second harmonic generation efficiency of 700 %/W achieves tunable wavelength conversion with a wavelength-tuning range of at least 25 nm through cascaded sum- and difference-frequency generation (SFG-DFG) process in which the signal and pumps are located symmetrically around the phase matching wavelength. The power penalty of the wavelength conversion is less than 0.6 dB for 43-Gb/s nonreturn-to-zero on-off-keying (NRZ-OOK) signals. We then apply the tunable wavelength conversion without SI to the parametric tunable dispersion compensation scheme, and achieve successful optical tunable dispersion compensation in 43-Gb/s NRZ-OOK transmissions over 53.2-km SMF.

Efficient lithium niobate waveguide for wide-dynamic-range wavelength conversion

We report an accurate measurement of χ(2) nonlinear optical effects and wide wavelength-conversion dynamic range of 50 dB in lithium niobate waveguide. Linear responses of DF power to pump and signal light are also obtained.

Parametric tunable dispersion compensator using cascaded sum- and difference-frequency generation of PPLN waveguide

We experimentally demonstrate parametric tunable dispersion compensation with a spectrally non-inverting tunable wavelength converter based on cascaded sum- and difference-frequency generation of PPLN waveguide. An error-free 43-Gbit/s NRZ-OOK transmission over 53.2km SMF is successfully achieved with a low-power penalty.

Opto-fluidic characterization of nonlinear-optical waveguide

Opto-fluidic technique demonstrated non-destructive characterization of nonlinear optical waveguide by modifying effective index of optical mode. Nonuniformity of phase matching wavelength, degradation factor of NLO performance, is revealed in a waveguide wavelength converter.

A 2.25-mW/Gb/s 80-Gb/s-PAM4 linear driver with a single supply using stacked current-mode architecture in 65-nm CMOS

This paper presents a low-power linear driver for a coherent optical transmitter. We propose a driver using stacked current-mode architecture to achieve low-power consumption with a single supply. The driver can drive from 25 to 50 Ω impedances with almost the same output waveforms by using a variable equalizer and adjusting the current of the post-amplifier. The proposed driver was fabricated in 65-nm CMOS technology and achieved the power efficiency of 3.6 mW/Gb/s with a differential output swing of 2.9 Vpp for a 50-Gb/s NRZ signal and 2.25 mW/Gb/s with a differential output swing of 2.0 Vpp for an 80-Gb/s PAM4 signal.

Design and Fabrication of Mixed Electronics-Optics Modulator for Dual-Carrier QPSK Generation

We discuss in detail the design and fabrication of a mixed electronics-optics (MEO) modulator and related key devices. Our proposed MEO modulator generates dual-carrier quadrature phase-shift keying (QPSK) signals utilizing both analog electrical and optical modulation with a simple optical circuit configuration. The key devices for the MEO modulator include a high-speed electrical-phase modulator and a complex optical modulator. We report the design and fabrication of a high-speed phase modulator IC with 0.5-μm InP HBT technology, and a silica-LiNbO3 integrated optical amplitude and phase modulator. We performed proof-of-concept experiments for the MEO modulator, and confirmed the generation of 26-GHz spacing 14-GBaud dual-carrier QPSK signals.

CW-pumped +11.6 dB gain in DFG using an efficient QPM adhered-ridge waveguide

We recorded the maximum channel conversion efficiency of +11.6 dB in DFG with 330 mW CW pump using Mg:LiNbO3-based QPM adhered-ridge-waveguide wavelength converter and discussed theoretical conversion efficiency for nonlinear optical effects.

Achromatically coupled wavelength conversion module with SILICAGRIN® lens

We develop a parametric wavelength conversion module with low chromatic dispersion using SILICAGRIN® optical fiber condenser. Less than 1 dB of the insertion loss difference between wavelength 780 nm and 1550 nm is achieved.

Waveguide parametric amplifier in quasi-phase-matched Mg:LiNbO3

CW parametric amplification is reported with adhered-ridge waveguide (ARW) of Mg-doped lithium niobate. Parametric gain of 13.6 dB is obtained at eye-safe 1.5 µm wavelength at a pump power as low as 330 mW.