Jimyung Kim

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.

Narrow linewidth operation of buried-heterostructure photonic crystal nanolaser

We investigate the spectral linewidth of a monolithic photonic crystal nanocavity laser. The nanocavity laser is based on a buried heterostructure cavity in which an ultra-small InGaAsP active region is embedded in an InP photonic crystal. Although it was difficult to achieve narrow linewidth operation in previously reported photonic crystal nanocavity lasers, we have successfully demonstrated a linewidth of 143.5 MHz, which is far narrower than the cold cavity linewidth and the narrowest value yet reported for nanolasers and photonic crystal lasers. The narrow linewidth is accompanied by a low power consumption and an ultrasmall footprint, thus making this particular laser especially suitable for use as an integrated multi-purpose sensor.

Optical and RF stability transfer in a monolithic coupled-cavity colliding pulse mode-locked quantum dot laser

We report a novel quantum dot based laser design where a stable high-Q master laser is used to injection lock a passively mode-locked monolithic colliding pulse slave laser. Coupling between the crossed orthogonal laser cavities is achieved through a common monolithically integrated saturable absorber, which results in the locking and hence reduction of the timing jitter as well as the long-term frequency drift of the slave laser. A stable 30 GHz optical pulse train is generated with more than 10 dB reduction in the RF noise level at 20 MHz offset and close to 3 times reduction in the 10 dB average optical linewidth of the slave laser.

Above threshold spectral dependence of linewidth enhancement factor, optical duration and linear chirp of quantum dot lasers.

The spectral dependence of the linewidth enhancement factor above threshold is experimentally observed from a quantum dot Fabry-Pérot semiconductor laser. The linewidth enhancement factor is found to be reduced when the quantum dot laser operates approximately 10 nm offset to either side of the gain peak. It becomes significantly reduced on the anti-Stokes side as compared to the Stokes side. It is also found that the temporal duration of the optical pulses generated from quantum dot mode-locked lasers is shorter when the laser operates away from the gain peak. In addition, less linear chirp is impressed on the pulse train generated from the anti-Stokes side whereas the pulses generated from the gain peak and Stokes side possess a large linear chirp. These experimental results imply that enhanced performance characteristics of quantum dot lasers can be achieved by operating on the anti-Stokes side, approximately 10 nm away from the gain peak.

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.

Interband optical pulse injection locking of quantum dot mode-locked semiconductor laser.

We experimentally demonstrate optical clock recovery from quantum dot mode-locked semiconductor lasers by interband optical pulse injection locking. The passively mode-locked slave laser oscillating on the ground state or the first excited state transition is locked through the injection of optical pulses generated via the opposite transition bands, i.e. the first excited state or the ground state transition from the hybridly mode-locked master laser, respectively. When an optical pulse train generated via the first excited state from the master laser is injected to the slave laser oscillating via ground state, the slave laser shows an asymmetric locking bandwidth around the nominal repetition rate of the slave laser. In the reverse injection case of, i.e. the ground state (master laser) to the first excited state (slave laser), the slave laser does not lock even though both lasers oscillate at the same cavity frequency. In this case, the slave laser only locks to higher injection rates as compared to its own nominal repetition rate, and also shows a large locking bandwidth of 6.7 MHz.

Interband optical pulse injection locking of quantum dot mode-locked semiconductor laser

We experimentally demonstrate that the slave laser oscillating on the ground state (GS) or excited state (ES) transitions can be locked through the injection of optical pulses generated via the opposite transition bands, i.e. the ES or GS transition, respectively.

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