Ricardo Rosales

High performance mode locking characteristics of single section quantum dash lasers.

Mode locking features of single section quantum dash based lasers are investigated. Particular interest is given to the static spectral phase profile determining the shape of the mode locked pulses. The phase profile dependence on cavity length and injection current is experimentally evaluated, demonstrating the possibility of efficiently using the wide spectral bandwidth exhibited by these quantum dash structures for the generation of high peak power sub-picosecond pulses with low radio frequency linewidths.

InAs/InP Quantum-Dot Passively Mode-Locked Lasers for 1.55-μ m Applications

This paper reports on recent results on passively mode-locked InAs/InP quantum-dot-based lasers. These low-dimensional structures have proved very attractive in improving most of the properties of these devices. Subpicosecond pulse generation at repetition rates up to beyond 300 GHz has readily been demonstrated. Ultranarrow RF linewidths reach record values of less than 1 kHz. Controlled optical feedback allows a further reduction of this linewidth yielding extremely low timing jitter. A comparison of single-section and standard two-section lasers is given for the first time. These performances open the way to various applications at 1.55 μm, including very high bit rate all-optical signal processing, frequency comb generation, radio over fiber, and low-noise all-optical oscillators.

Injection-Locking Properties of InAs/InP-Based Mode-Locked Quantum-Dash Lasers at 21 GHz

We report optical injection-locking in 21-GHz single-section and two-section InAs/InP 1.5-μm quantum-dash mode-locked lasers. Two distinct mode-locked regimes were observed and successfully locked to the optically injected light. The single-section laser only operates as a self-mode-locked laser while the two-section laser could operate as both a self-mode-locked laser and saturable-absorber dominated mode-locked laser. The continuous-wave (CW) injection-locked self-mode-locked laser shows wide tuning of the mode-locked frequency (≈270 MHz) within the locking range. The CW injection-locked saturable-absorber dominated mode-locked laser demonstrates wide optical spectrum, and 5.5 × reduction in the time-bandwidth product of the pulses. Using dual-mode injection, strong reduction of timing jitter ( ≈235 fs) is possible leading to the generation of a wide coherent frequency comb. Coherence between all the modes and the master laser is confirmed by measuring the RF beat note of each mode with a narrow linewidth laser.

Stability of Optical Frequency Comb Generated With InAs/InP Quantum-Dash-Based Passive Mode-Locked Lasers

In this paper, we present a systematic investigation of passive mode-locked InAs/InP quantum-dash lasers in terms of frequency and timing stability. Mode-locking features are analyzed using the frequency domain approach based on the concept of supermodes. It is shown that the phase of adjacent longitudinal modes is correlated over 1.3-THz frequency span. The observed strong coherence between modes enables low timing jitter and a long-term stability of the repetition rate frequency within 5×10-8 over 100 s.

A Novel Scheme for Two-Level Stabilization of Semiconductor Mode-Locked Lasers Using Simultaneous Optical Injection and Optical Feedback

We introduce a novel scheme for the simultaneous reduction of time-bandwidth product (TBP) and RF linewidth of quantum-dash two-section mode-locked lasers using optical injection-locking and filtered optical feedback. The optical injection-locked laser, double-locked with optical feedback showed 2× TBP reduction and RF linewidth reduction by two orders of magnitude. This stabilization technique is implemented in an all-optical arrangement without optical/electrical conversion which is ideal for high-repetition-rate devices and photonic integration.

Optical pulse generation in single section InAs/GaAs quantum dot edge emitting lasers under continuous wave operation

Observation of sub-picosecond pulses from a single section Fabry Perot InAs/GaAs edge emitting quantum dot (QD) based laser at 1.3 μm under continuous wave operation is reported. After group delay dispersion compensation, pulse durations as short as 770 fs in a 45 GHz repetition rate device have been measured, with 1.9 W of peak power and a narrow radio frequency spectrum of only a few kHz linewidth. The experiments show evidence of an unexplored mode locking regime in the InAs/GaAs quantum dot material system, which still needs theoretical modelling and further analysis.

Mode coherence measurements across a 1.5 THz spectral bandwidth of a passively mode-locked quantum dash laser

The mode coherence of adjacent and non-adjacent spectral modes of a passively mode locked quantum dash (QDash) semiconductor laser are deduced through radio frequency beat-tone linewidth measurements. A wavelength conversion scheme that uses degenerate four wave mixing in a semiconductor optical amplifier is proposed which considerably extends the mode spacing beyond the limit imposed by conventional fast-photodetection and electrical spectrum analysis of around 100 GHz. Using this scheme, the mode coherence of the QDash laser was measured out to the thirty-first harmonic, or a mode separation of 1.5 THz.

1.9 W continuous-wave single transverse mode emission from 1060 nm edge-emitting lasers with vertically extended lasing area

High-brightness edge-emitting semiconductor lasers having a vertically extended waveguide structure emitting in the 1060 nm range are investigated. Ridge waveguide (RW) lasers with 9 μm stripe width and 2.64 mm cavity length yield highest to date single transverse mode output power for RW lasers in the 1060 nm range. The lasers provide 1.9 W single transverse mode optical power under continuous-wave (cw) operation with narrow beam divergences of 9° in lateral and 14° (full width at half maximum) in vertical direction. The beam quality factor M2 is less than 1.9 up to 1.9 W optical power. A maximum brightness of 72 MWcm−2sr−1 is obtained. 100 μm wide and 3 mm long unpassivated broad area lasers provide more than 9 W optical power in cw operation.

Timing jitter from the optical spectrum in semiconductor passively mode locked lasers

An analysis of the passively mode locked regime in semiconductor lasers is presented, leading to an explicit expression relating the timing jitter diffusion constant to the optical linewidths in these devices. Experimental results for single section quantum-dash based lasers validating the theoretical analysis are presented for the first time. Timing jitter of mode locked lasers at rates of up to 130 GHz has been experimentally estimated from the optical spectra without requiring fast photodetection.

Frequency resolved optical gating characterization of sub-ps pulses from single-section InAs/InP quantum dash based mode-locked lasers

Mode-locking of single-section Fabry-Pérot InAs/InP edge emitting quantum dash based lasers at 1.56 µm under continuous wave operation is studied by second-harmonic generation frequency resolved optical gating. Self-starting pulses of a width down to 374 fs can be observed after external chirp compensation using standard single-mode fiber (SMF-28). Pulse compression using different lengths of SMF-28 and pulse shape as well as phase dependence on bias conditions are investigated. Consistency with stepped-heterodyne technique for advanced pulse characterization is shown.