Yong-Soon Baek

ALL-OPTICAL SWITCHING IN A HYBRID MACH-ZEHNDER INTERFEROMETER AS A RESULT OF CASCADED SECOND-ORDER NONLINEARITY

We demonstrate, for the first time to our knowledge, all-optical switching with a contrast ratio of 7:1 based on the cascaded second-order nonlinearity. We performed the switching experiments in a nonlinear hybrid Mach–Zehnder interferometer, using a nonuniformly temperature-tuned lithium niobate channel waveguide in an operating regime of small fundamental depletion.

ALL-OPTICAL SWITCHING IN LITHIUM NIOBATE DIRECTIONAL COUPLERS WITH CASCADED NONLINEARITY

We report on intensity-dependent switching in lithium niobate directional couplers. Large nonlinear phase shifts that are due to cascading detune the coupling between the coupler branches, which makes all-optical switching possible. Depending on the input intensity, the output could be switched between the cross and the bar coupler branches with a switching ratio of 1:5 and a throughput of 80%.

Direct measurement of cascaded nonlinearity in lithium niobate channel waveguides.

We report on interferometric measurements of nonlinear phase shifts of the fundamental mode that are due to cascading in a second-harmonic-generation experiment in lithium niobate channel waveguides. With temperature tuning of the wave-vector mismatch the nonlinear phase shifts were adjustable in sign and magnitude. Varying the wave-vector matching condition along the waveguide leads to large phase shifts with low depletion and dispersion of the fundamental.

Interactions between one-dimensional quadratic solitons

The interaction between two one-dimensional quadratic solitons has been investigated experimentally in lithium niobate planar waveguides for both parallel- and crossing-launched solitons.

All-optical integrated Mach-Zehnder switching due to cascaded nonlinearities

This paper reports all optical switching in a fully integrated Mach-Zehnder interferometer due to the cascaded second order nonlinearities with a switching ratio of 8:1. Along with the lithium niobate directional coupler, these represent the first integrated all-optical switching devices using cascaded second order nonlinearities. By using a higher X2 material and/or quasiphase-matching techniques independently for each channel, the switching power can be reduced by orders of magnitude.

Multiwavelength Lasers for WDM-PON Optical Line Terminal Source by Silica Planar Lightwave Circuit Hybrid Integration

We have demonstrated a very compact eight-channel 200-GHz-spacing multiwavelength laser (MWL) module for the optical line terminal source of wavelength-division-multiplexing passive optical network. The wavelength shift of MWLs and external cavity lasers from the ITU grid was within +0.14 nm for eight channels, which was well matched to the target wavelength shift of less than plusmn0.2 nm. The oscillation characteristics of our MWL module are better than those of conventional MWLs with hybrid integration.

One-dimensional quadratic walking solitons

The properties of one-dimensional quadratic walking solitons were investigated in planar lithium niobate waveguides near the type I phase-matching condition for second-harmonic generation. Wave propagation was studied under different conditions of phase matching, walk-off angle, and incident fundamental power.

High-Performance 1.55-

We report the design and fabrication of a novel 1.55-m spot-size converter superluminescent diode (SLD) for optical access networks. The active section of SLD was fabricated by using a planar buried heterostructure to adopt the double-waveguide-core structure for low-threshold and high-output power operation at a low injection current. A ridge-based passive waveguide was employed for an efficient coupling to a planar lightwave circuit. The threshold current was as low as 14 mA, and the maximum output power was as high as 28 mW with ripple less than 3 dB at an injection current of 200 mA.

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We present a new configuration of a thin-film-filter (TFF)-embedded planar-light-circuit platform for a bidirectional transceiver module to enhance a tolerance of the insertion loss to the positional deviation of the TFF, by using a wide multimode waveguide structure that guides a reflected light from the TFF to a photoreceiver. It is experimentally shown that the new scheme has a merit in a high tolerance to the positional deviation of the TFF, and that it maintains a considerably high optical isolation by a proper arrangement of waveguides.

m Superluminescent Diode With Butt-Coupled Spot-Size Converter

The interaction between two quadratic soliton-like beams was investigated for beams launched parallel to one another, and at small crossing angles. The experiments were performed in titanium in-diffused lithium niobate slab waveguides near a Type I phase-matching condition for second harmonic generation (SHG). Only beams at the fundamental frequency were launched and the second harmonic required for quadratic soliton formation was generated upon propagation into the waveguide. The results of the interaction were found to depend on the relative phase between the input fundamental beams, the net phase mismatch for SHG and on the beam crossing angle. Good agreement with numerical simulations of the different interactions was found. In general, the results of the interactions were similar to those found in saturable Kerr-like media.