Chi-Luen Wang

TUNABLE MULTITERAHERTZ BEAT SIGNAL GENERATION FROM A TWO-WAVELENGTH LASER-DIODE ARRAY

We report, for the first time to our knowledge, generation of a tunable miltiterahertz modulation signal on an optical carrier directly from a single laser source. The modulation frequency, which can be tuned from 0.15 THz to more than 7 THz, is the beat note obtained by varying the spectral separation between the coaxial two-color output of a two-wavelength laser-diode array from 0.32 to 17 nm. The frequency characteristics of the terahertz beat note are determined with a noncollinear intensity autocorrelator.

Supercontinuum generation by noise-like pulses transmitted through normally dispersive standard single-mode fibers

We report generation of broadband supercontinuum (SC) by noise-like pulses (NLPs) with a central wavelength of 1070 nm propagating through a long piece of standard single-mode fibers (~100 meters) in normal dispersion region far from the zero-dispersion point. Theoretical simulations indicate that the physical mechanism of SC generation is due to nonlinear effects in fibers. The cascaded Raman scattering is responsible for significant spectral broadening in the longer wavelength regions whereas the Kerr effect results in smoothing of SC generated spectrum. The SC exhibits low threshold (43 nJ) and a flat spectrum over 1050-1250 nm.

TUNABLE DUAL-WAVELENGTH OPERATION OF A DIODE-ARRAY WITH AN EXTERNAL GRATING-LOADED CAVITY

A novel grazing‐incidence grating cavity has been developed for simultaneous generation of laser output at two wavelengths. The gain section is a commercial laser diode array. By moving vertically with respect to the optical axis V‐shaped double slit at the end mirror, we demonstrate tuning of the spectral separation of the dual‐wavelength laser output from 3.52 to 11.29 nm. The side‐mode suppression ratio is 10–20 dB. Examination of the far‐field patterns reveal that the laser mode at the two wavelengths corresponds to a different order of the array modes.

A self-protected colorless WDM-PON with 2.5 Gb/s upstream signal based on RSOA

In this investigation, we propose and demonstrate a colorless wavelength division multiplexed passive optical network (WDM-PON) at 2.5 Gb/s using reflective semiconductor optical amplifier (RSOA)-based optical networking units (ONUs); together with a self-protected architecture against fiber fault. In the optical line terminal (OLT), we use an array of self-seeding Fabry-Perot laser diodes (FP-LDs) to provide single-longitudinal-mode (SLM) continuous wave (CW) optical sources for the external injection to the RSOA-based ONUs. The self-survivable function for protecting the fiber fault in the distributed fibers and the proposed network performance are investigated and discussed.

Dual-wavelength actively mode-locked laser-diode array with an external grating-loaded cavity

We report the generation of dual-wavelength picosecond pulses by use of a commercial laser-diode array. The laser cavity incorporated a folded dispersive delay line with a V-shaped double-stripe mirror. The spectral separation of the laser output at the two wavelengths can be tuned from 2 to 11 nm. The actively mode-locked pulse widths at the two wavelengths were both 29 ps. Cross-correlation and power-spectrum measurements indicated that the two-color pulses were synchronized with an absolute timing jitter of less than 1 ps (instrument limited).

Two-wavelength interferometer based on a two-color laser-diode array and the second-order correlation technique

A novel two-wavelength interferometer is demonstrated that uses a tunable two-color laser-diode array as the light source. The synthetic wavelength can be easily tuned from 2 to 0.043 mm by variation of the spectral separation between the two wavelengths of the laser output. By using the second-order correlation technique we can directly retrieve the phase change at the synthetic wavelength with no need for sophisticated electronic signal processing.

Broadly tunable self-starting passively mode-locked Ti:sapphire laser with triple strained-quantum-Well saturable Bragg Reflector

Abstract We demonstrate broadband mode-locking of femtosecond Ti:sapphire lasers with a new type of saturable Bragg reflector (SBR). Triple-strained quantum wells with separate and sequential bandgaps were used as the absorbing layer. The saturation fluence was as low as 7 μJ/cm 2 . Self-starting sub-100 fs pulses tunable from 768 to 804 nm were generated in a standard X-folded cavity without intracavity tight focusing on the SBR or temperature tuning. The threshold fluence for self-starting mode-locking was 1 μJ/cm 2 .

Demonstration of high spectral efficient OFDM-QAM long reach passive optical network

We demonstrate a high spectral-efficient LR-PON using 4 Gb/s OFDM-QAM for both up-and-downstream, achieving a high split-ratio 256, using optical components optimized for GPON.

Robust diode-end-pumped Nd:GdVO4 laser passively mode-locked with saturable output coupler

Passively mode-locked diode-pumped solid-state (DPSS) Nd:GdVO4 laser by using a saturable output coupler (SOC) in stable two-mirror linear cavity design is demonstrated. The laser was pumped by low-power single laser diode without any active cooling and external optics. Robust CW mode-locked operation was obtained with a repetition of 150–250 MHz, the pulsewidth was 12 ps, the lowest threshold for CW mode-locked was 185 mW. The optimal condition is found when the laser provides the set of characteristics: low CW mode-locking threshold (∼260 mW), compact size (total cavity length 60 cm), good efficiency (∼20%), and very stable output. At the output power of 270 mW an average power fluctuations within ±2% for long-term operation was obtained.

Bidirectional ROF transmission and signal remodulation using separate optical clock distribution to mitigate signal distortions

We demonstrate a bidirectional ROF system using a separate optical-clock distribution to mitigate signal-fading and code time-shifting. Error-free signal remodulation using downlink DPSK and uplink OOK was achieved in a 20-km reach ROF system.