Myoung-Taek Choi

Optical frequency combs from semiconductor lasers and applications in ultrawideband signal processing and communications

Modelocked semiconductor lasers are used to generate a set of phase-locked optical frequencies on a periodic grid. The periodic and phase coherent nature of the optical frequency combs makes it possible for the realization of high-performance optical and RF arbitrary-waveform synthesis. In addition, the resulting optical frequency components can be used for communication applications relying on direct detection, dense wavelength division multiplexing (WDM), coherent-detection WDM, optical time-division multiplexing, and optical code division multiple access. This paper highlights the recent results in the use of optical frequency combs generated from semiconductors for ultrawideband signal processing and communication applications.

Ultrashort, high-power pulse generation from a master oscillator power amplifier based on external cavity mode locking of a quantum-dot two-section diode laser

We investigate an external cavity curved two-section mode-locked diode laser system based on quantum-dot (QD) gain media near 1.3μm. Pulses are generated from the external laser cavity at a 5‐GHz repetition rate and amplified using a multilayer quantum-dot semiconductor optical amplifier. The pulses are compressed with a dual-grating dispersion compensator. The shortest, near transform-limited pulses are obtained when the mode-locked pulses are positive (up) chirped. The compressed pulses are 1.2ps in duration, with a pulse energy of 1.46pJ, implying a peak power of 1.22W.

Pulse generation and compression via ground and excited states from a grating coupled passively mode-locked quantum dot two-section diode laser

The authors generate and compress short pulses via the ground and excited state transitions from a passively mode-locked grating coupled quantum dot two-section diode laser at a repetition rate of 2.7GHz. The selection and isolation of either the ground state or excited state transition were performed by an angle tuning of the grating. The externally compressed pulse widths are 970fs from the ground state and 1.2ps from the excited state transition. The sign of the chirp is up chirped for both state transitions.

Ultralow noise optical pulse generation in an actively mode-locked quantum-dot semiconductor laser

We report excellent noise performance of an external-cavity actively mode-locked laser based on quantum-dot gain medium. Optical pulse trains with less than 7.5fs residual timing jitter (1Hzto10MHz) for a 12.8GHz harmonically mode-locked ring laser were obtained. This result represents, to our knowledge, the lowest residual jitter reported from actively mode-locked semiconductor lasers, and shows that quantum-dot mode-locked lasers are promising as sources of ultralow noise optical pulse trains.

Wavelength tunable mode-locked quantum-dot laser

We study the characteristics of wavelength tunable quantum-dot mode-locked lasers using a curved two-section device, external grating, and optical bandpass filter. Wide wavelength tunability is demonstrated due to the fact that the center wavelength of mode-locking is extended to excited state transitions as well as ground state transitions of the quantum-dot gain media.

Modelocked diode lasers for ultra-wideband communications and signal processing

Modelocked semiconductor lasers are used to generate a set of phase locked optical frequencies on a periodic grid. The resulting optical frequency components can be used for communication applications relying on direct detection, dense WDM, coherent detection WDM, OTDM, and OCDMA. In addition, the periodic and phase coherent nature of the optical frequency combs make it possible for the realization of high performance optical and RF arbitrary waveform synthesis. This paper highlights recent results in the use of optical frequency combs for ultrawideband communication and signal processing applications.

Pulse generation and compression via ground and excited state from a grating coupled quantum dot external cavity mode locked laser

We generate and compress short pulses via the ground and excited state transitions from a grating coupled quantum dot external cavity mode locked laser. The sign of the chirp is similar for both transitions

Linewidth enhancement factor reduction on the blue side of the gain peak from a quantum dot mode-locked laser

We observed above threshold linewidth enhancement factor reduction at blue side lasing wavelengths from a quantum dot mode-locked laser. The linewidth and pulse width become narrower as the lasing wavelength is tuned to blue side.

Recent Advances in Stabilized Ultrafast Modelocked Semiconductor Diode Lasers for High Speed Information Based Applications

Novel cavity engineering techniques are used to realize low noise, and stabilized optical frequency combs from quantum well and quantum dot based modelocked semiconductor diode lasers. Applications in high speed signal processing, secure communications and arbitrary waveform generation are highlighted

Coherent Homodyne Pulse Detection for a Spectral Phase-Encoded Optical CDMA System Using Synchronized Modelocked Lasers

The performance of coherent homodyne pulse detection of a synchronized modelocked semiconductor laser system is experimentally demonstrated. The numerical and experimental results of enhanced detection sensitivity with an improved SNR are reported.