Sahnggi Park

Si micro-ring MUX/DeMUX WDM filters

We demonstrate 3rd order micro-ring filters, 100 GHz-spaced 16 channels and 50 GHz-spaced 32 channels. Fabrication-induced resonant wavelength errors, σ = 0.237 nm, and temperature-dependent wavelength shift, 0.043 nm/°C tolerable to ΔT>10 °C, has been measured on filters based on the fundamental TM mode. The problem of CMOS-compatible photolithography is solved, while maintaining a small radius, R = 9 μm. As some dummy channels are arranged, it is shown that an on-chip optical network for many cores CPU can be constructed by 16 channel ring filters with the currently available technology.

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.

The design and the fabrication of monolithically integrated GaInAsP MQW laser with butt-coupled waveguide

We optimized the etching process for butt coupling to improve the reproducibility and the uniformity of the process for the integrated GaInAsP multiquantum-well laser with a butt-coupled waveguide. Three different ways of etching process were tested, which are reactive ion etching (RIE), RIE followed by a small amount (50 nm thick) of selective wet etching, and RIE followed by an adequate amount (125 nm thick) of selective wet etching. RIE followed by an adequate amount of selective wet etching showed the superior properties to the common expectation on RIE only, giving the measured coupling efficiency 96/spl plusmn/1.7% versus 34/spl plusmn/8%. The high coupling efficiency and the very small variation across a quarter of a 2-in wafer demonstrate that RIE coupled with an adequate amount of selective wet etching can also replace the conventional process for butt coupling, RIE followed by HBr-based nonselective wet etching, to fabricate high-quality integrated photonic devices.

Fabrication of InGaAsP/InP Two-Dimensional Periodic Nanostructure with Variable Sizes and Periods Using Laser Holography and Reactive Ion Etching

Two-dimensionally arrayed nanocolumns of InGaAsP/InP were fabricated using double-exposure laser holography and reactive ion etching (RIE). The size and period of nanocolumns could be controlled accurately from 80 to 150 nm in diameter and 220 to 450 nm in period by changing the incident angle of the laser beam. RIE for a typical time of 30 min using CH 4 /H 2 plasma enhanced the aspect ratio by more than 1.5 with a slight increase of the bottom width of columns. Furthermore, a wet-treatment after RIE showed a large enhancement of photoluminescence intensity, suggesting that the damage was cured effectively on the sidewalls of the nanocolumns.

Fabrication of wavelength-tunable butt-coupled sampled grating DBR lasers using planar buried heterostructure

Planar buried heterostructure (PBH) was adopted to fabricate a sampled grating distributed Bragg reflector laser diode (SGDBR-LD) having a low threshold current and a stable fundamental transverse mode. The etching process for butt-coupling was optimized to improve the reproducibility and the uniformity of the butt-coupled waveguide. The maximum output power of the fabricated SGDBR-LD was 20 mW at 200-mA continuous-wave operation at 25/spl deg/C. The output power was measured 10 and 9 mW higher than those of ridged waveguide (RWG) structure and buried ridge stripe (BRS), and the threshold current was slightly higher than those of RWG and BRS. The spectra of 25 channels spaced 50 GHz within the tuning range of 44.4 nm was obtained by a precise control of SG and phase control currents. The side-mode suppression ratio of more than 35 dB was obtained in the whole tuning range. The output power variation was less than 5 dB, which is 4 dB smaller than that of RWG structure.

Adjusting resonant wavelengths and spectral shapes of ring resonators using a cladding SiN layer or KOH solution.

It is shown that the resonant frequencies and the transmission spectra of ring resonators can be adjusted by depositing or etching the cladding nitride layer on the ring waveguide without introducing an extra loss or extra variations of channel spacing. The cladding nitride layer increases the minimum width of the gap in the coupling region to larger than 150nm which makes it possible to consider photolithography instead of E-beam lithography for the typical design rule of ring filters. KOH silicon etching can also adjust not only the resonance frequencies but also coupling coefficients with a small sacrifice of guiding loss.

Fabrication of WDM-PON OLT Source using External Cavity Laser

A very compact 16-channel 200 GHz-spacing transmitter module was fabricated for wavelength division multiplexing-passive optical network (WDM-PON) optical line termination (OLT) source. The transmitters are composed of reflection gratings and hybrid integrated superluminescent laser diodes (SLD) to construct 16-channel external cavity lasers (ECLs) on the planar lightwave circuit (PLC) chip.

Echelle grating silicon multi/demultiplexers with single-reflection total internal reflectors

We present a silicon-on-insulator Echelle grating 8-channel demutiplexer showing characteristic features, average insertion loss 2.4 dB measured at 1520~1570 nm, adjacent channel crosstalk 15-18 dB, and channel spacing 11.9 nm. Our Echelle grating is remarked by a total internal reflector (TIR) which reflects incident light by a single reflection in contrast to the double reflections of retro-reflector TIR Echelle gratings.

Thermally controlled wavelength locker integrated in widely tunable SGDBR-LD module

A sampled-grating distributed Bragg reflector laser module having an integrated multiwavelength locker has been developed and evaluated. The uniquely designed wavelength locker made of thermally controlled etalon has provided uniform wavelength monitoring and very stable wavelength locking in the 188-ITU grid channels (37 nm) with 25-GHz spacing. Over the case temperature from -5/spl deg/C to 65/spl deg/C, the laser wavelength was locked within /spl plusmn/0.5 GHz, and the total power consumption of the module was less than 4 W.

Fabrication of Tunable Sampled Grating DBR Laser Integrated Monolithically with Optical Semiconductor Amplifier Using Planar Buried Heterostructure

We have demonstrated a high-power widely tunable sampled grating (SG) DBR laser integrated monolithically with optical semiconductor amplifier (SOA), using planar buried heterostructure (PBH). The measured threshold current was 5 mA on average with 60 chips randomly selected which is lowest among the typical average values. Fiber-coupled output power was 12.4 dBm and the output power variation was ?1 dB for the whole tuning range.