Hyun-kuk Shin

Vertical-Cavity Surface-Emitting Lasers for Optical Data Storage.

The application of vertical-cavity surface-emitting laser (VCSEL) diodes for optical data storage has been investigated. VCSELs suitable for compact disc optical heads have been designed and fabricated. A photo diode for optical power monitoring is integrated in a VCSEL chip, and a holographic optical head using VCSEL is also manufactured. Single transverse mode operation up to 1.5 mW shows good performance.

Reflective SOAs optimized for 1.25 Gbit/s WDM-PONs

We present R-SOAs with improved modulation bandwidth of /spl sim/1.35 GHz as WDM sources in 1.25 Gbit/s WDM-PONs. In back-to-back transmission using the R-SOA seeded by 0.6 nm-wide ASE of -20 dBm, receiver sensitivity at a 10/sup -9 /BER was - 25.3 dBm.

Reliability in the oxide vertical-cavity surface-emitting lasers exposed to electrostatic discharge

Electrostatic discharge(ESD) damage is known as a major source affecting the lifetime of oxide VCSEL. We investigated how ESD damage threshold voltage depends on the size, thickness, and composition of the oxide aperture by measuring the change of output power and reverse leakage current after ESD. ESD damage threshold voltage increased with the size of the oxide aperture, regardless of the thickness and the composition of the oxide aperture. However, damaged devices with thinner oxide layers showed relatively longer lifetime in the reliability test. The reliability data also showed that the VCSELs exposed to ESD have steeper power declines in reliability test than normal devices. This may be due to the defects formed in the active medium by ESD.

Polarization-independent, high-power, and angle-flared superluminescent diode for WDM-PON applications

We developed polarization-independent high-power superluminescent diodes (SLDs) for wavelength division multiplexed-passive optical network (WDM-PON) applications. The SLD presents CW output power of 150 mW, spectral bandwidth of 40 nm, polarization-dependent power variation of less than 1 dB, and spectral ripple of 3 dB at current of 1.47 A and temperature of 25 degC

Demonstrateion of DWDM-PON Employing Spectrum-sliced RSOA over 90-°C Temperature Range

A WDM-PON with 50-GHz channel spacing employing RSOA-based spectrum sliced sources is presented. Colorless operations over 32 DWDM channels are demonstrated from -10 to 80 °C in 155-Mb/s transmissions over 10 km.

Low-Cost CWDM Transceiver Module by Spatial Power Combination and Division for Multimode Fiber Links

A cost-effective coarse wavelength division multiplexing optical sub-assembly (OSA) for short-distance optical interconnection is proposed and fabricated. Filter-free transmitter multiplexing is demonstrated by a spatial power combination of multiple-wavelength laser outputs into a fiber. As a result, the OSA is constructed with a reduced burden in optical alignment and packaging owing to the small number of optical elements and large alignment tolerance. Data transmission with a bit rate of 6 Gb/s is achieved through a 100-m-long multimode fiber. No significant degradation of eye patterns is observed during the transmission, and a bit error rate below 10-12 is attained with the proposed module.

Demonstration of WDM-PON using spectrum-sliced RSOA

We present a low-cost WDM-PON employing colorless uncooled RSOA-based spectrum sliced sources. Colorless operations over 32 WDM channels are demonstrated from 0 to 60 oC in 155-Mb/s transmissions over 25 km.

Strong polarization selectivity in 780-nm vertical-cavity surface-emitting lasers grown on misoriented substrates

We report that the 780 nm quantum well vertical-cavity surface-emitting lasers ~VCSELs! grown on a 2° off misoriented ~001! substrate toward ~111!A exhibit a high polarization suppression ratio over a few hundred. The main polarization is always along the @2110# direction for all the lasers over the entire operating currents. To understand the physical origin of this polarization selectivity, the gain/loss difference between two competing polarization modes in VCSELs is investigated by measuring the subthreshold spectral linewidth. The obtained modal gain/loss difference is about 3.0 cm, which is sufficiently large for polarization stabilization and amounts to 4% of the threshold modal gain. Comparison with the subthreshold measurement and previous theoretical work shows significant discrepancy, which implies the possibility of other polarization selection mechanisms inducing such large gain/loss differences in 780 nm quantum wells grown on a misoriented substrate. In addition, it is found that the 780 nm VCSEL made of a bulk active medium grown on a misoriented substrate also shows a high polarization selectivity as quantum well lasers.