Tomoyuki Kato

Investigation of all-optical latching operation of a monolithically integrated SOA-MZI with a feedback loop

We have investigated an all-optical set/reset and latching operation using a monolithically integrated InP-based semiconductor optical amplifier type Mach-Zehnder interferometer with a feedback loop. In simulation, operation conditions when both set and reset are possible was estimated for input light pulse with a FWHM of 31 and 12.5 ps, and the tolerance of the CW probe light and feedback loop loss becomes large with increasing the input light pulse power. In addition, the loop length could be longer than the distance of the light propagating in one bit pulse because of the longer carrier recovery time than one bit time duration. Moreover, we successfully achieved set/reset operation with 34- and 18-ps wide set/reset pulses.

All-optical flip-flop circuit based on SOA-MZI

Performance of all-optical flip-flop circuits based on a SOA-MZI is reviewed. Set-reset-type operation and T-type operation will be presented with feedback loop configuration for optical gate signal generation, and a counterfaced one for DPSK encoding, respectively.

Sub-harmonic mode-locking of VCSEL with a concave external mirror

We designed a composite resonator VCSEL using a VCSEL chip and a concave external mirror for mode-locking to produce optical clock signals and demonstrated the operation experimentally. A very low threshold current was successfully realized by using a proper reflectivity of VCSEL and the external mirror and by achieving efficient feedback using a concave external mirror. Using a concave mirror with the curvature radius of 14.12mm, sub-harmonic active mode-locking was achieved at a repetition rate of 10.56GHz, which corresponded to the external cavity length.

Experimental demonstration of an optical packet gating using a monolithically-integrated InP SOA-MZI-type all-optical flip-flop circuit with a feedback loop

We experimentally demonstrate an optical gating using cascaded monolithically integrated SOA-MZI-type all-optical flip-flop circuit with a feedback loop and an optical gate. Gating operation of optical packet at 10Gbps with an extinction ratio of 8.3dB was successfully achieved.

All-optical latch and gate pulse generation in all monolithically integrated SOA-MZI-type set/reset flip-flop using ultrashort optical pulses for 40Gbps operation

We achieved latch and gate pulse generation in a monolithically integrated semiconductor-optical-amplifier-based Mach-Zehnder interferometer-type set/reset flip-flop using ultrashort pulses. The operation of the device with 18-ps optical pulses for 40Gbps operation was verified under the condition of slow carrier recovery condition.

Actively mode-locked VCSEL module with double-path resonance configuration

Sub-harmonic actively mode-locked VCSEL module was successfully fabricated by fixing a concave mirror using UV cure adhesive. Unique double-path resonance configuration was found effective to relax the mirror misalignment tolerance.

Two-dimensionally parallel optical interconnects using VCSELs with an integrated lens

We propose multistage waveguide coupling scheme by using VCSELs with an integrated lens for onboard optical interconnection. We demonstrated the possibility of multistage coupling more than five stage and it indicates the higher-density parallel optical interconnection with a small footprint.

A study on all-optical packet path switching using wavelength conversion and dynamic response of a tunable laser for wavelength switching

We achieved optical flip-flop (FF) operation using an SOA-MZI with feedback loop for all-optical packet path switching. In addition, we investigated the dynamic characteristics of the lasing wavelength of the high-speed tunable laser, a SSG-DBR-LD for optical buffering.

High repetition rate and low threshold current mode-locked VCSEL using concave mirror

To realize low power consumption and high-speed repetition rate mode-locked laser, we designed a VCSEL with an external concave mirror. Repetition rate as high as 31 GHz and threshold current as low as 1 mA were simultaneously demonstrated with sub-harmonic active mode-locking.

Double-path resonance of a mode-locked VCSEL using a concave mirror

We have demonstrated mode-locking using a VCSEL and a concave mirror with new double-path resonance scheme. This scheme was found to provide significant improvement in the position tolerance between the VCSEL and the concave mirror.