Gain switching of an external cavity grating-coupled surface emitting laser with wide tunability

The gain-switched, single frequency operation of an external cavity grating-coupled surface emitting laser with a wavelength tuning range of 100 nm was presented. The light in the grating section was coupled out of the laser at a specific angle to the surface of the device. Analysis showed that within the driving current range, lasing in the device only occurred when the external cavity was properly aligned.

Broad wavelength tunability from external cavity quantum-dot mode-locked laser

Broadband wavelength tunability over 136 nm (between 1182.5 nm and 1319 nm) of picosecond pulses in passive mode-locked regime is demonstrated in a multi-section quantum-dot laser in external cavity configuration at room temperature. The maximum peak power of 870 mW with 15 ps pulse duration was achieved at 1226 nm wavelength. © 2012 American Institute of Physics.

High-power wavelength bistability and tunability in passively mode-locked quantum-dot laser

Wavelength bistability and tunability are demonstrated in a two-sectional quantum-dot mode-locked laser with a nonidentical capping layer structure. The continuous wave output power of 30 mW (25 mW) and mode-locked average power of 27 mW (20 mW) are achieved for 1245 nm (1295 nm) wavelengths, respectively, under the injection current of 300 mA. The largest switching range of more than 50 nm and wavelength tuning range with picosecond pulses and stable lasing wavelengths between 1245 and 1295 nm are demonstrated for gain current of 300 and 330 mA. © 1995-2012 IEEE.

Characterization of 45º-tilted fiber grating and its polarization function in fiber ring laser

We have proposed and demonstrated a fiber ring laser with single-polarization output using an intracavity 45°-tilted fiber grating (45°-TFG). The properties of the 45°-TFG have been investigated both theoretically and experimentally. The fiber ring laser incorporating the 45°-TFG has been systematically characterized, showing a significant improvement in the polarization extinction ratio (PER) and achieving a PER of >30 dB. The slope efficiencies of the ring laser with and without the 45°-TFG have been measured. This laser shows a very stable polarized output with a PER variation of less than 2 dB for 5 hours at laboratory conditions. In addition, we also demonstrated the tunability of the laser.

Stabilization of a passively mode-locked laser by continuous wave optical injection

We investigate numerically and experimentally the properties of a passively mode locked quantum dot semiconductor laser under the influence of cw optical injection. We demonstrate that the waveform instability at high pumping for these devices can be overcome when one mode of the device is locked to the injected master laser and additionally show spectral narrowing and tunability. Experimental and numerical analyses demonstrate that the stable locking boundaries are similar to these obtained for optical injection in CW lasers. © 2010 American Institute of Physics.

Mode-locked semiconductor lasers with optical injection

We perform characterization of the pulse shape and noise properties of quantum dot passively mode-locked lasers (PMLLs). We propose a novel method to determine the RF linewidth and timing jitter, applicable to high repetition rate PMLLs, through the dependence of modal linewidth on the mode number. Complex electric field measurements show asymmetric pulses with parabolic phase close to threshold, with the appearance of waveform instabilities at higher currents. We demonstrate that the waveform instabilities can be overcome through optical injection-locking to the continues wave (CW) master laser, leading to time-bandwidth product (TBP) improvement, spectral narrowing, and spectral tunability. We discuss the benefits of single- and dual-tone master sources and demonstrate that dual-tone optical injection can additionally improve the noise properties of the slave laser with RF linewidth reduction below instrument limits (1 kHz) and integrated timing jitter values below 300 fs. Dual-tone injection allowed slave laser repetition rate control over a 25 MHz range with reduction of all modal optical linewidths to the master source linewidth, demonstrating phase-locking of all slave modes and coherence improvement.

Mode-locked semiconductor lasers with optical injection

We perform characterization of the pulse shape and noise properties of quantum dot passively mode-locked lasers (PMLLs). We propose a novel method to determine the RF linewidth and timing jitter, applicable to high repetition rate PMLLs, through the dependence of modal linewidth on the mode number. Complex electric field measurements show asymmetric pulses with parabolic phase close to threshold, with the appearance of waveform instabilities at higher currents. We demonstrate that the waveform instabilities can be overcome through optical injection-locking to the continues wave (CW) master laser, leading to time-bandwidth product (TBP) improvement, spectral narrowing, and spectral tunability. We discuss the benefits of single- and dual-tone master sources and demonstrate that dual-tone optical injection can additionally improve the noise properties of the slave laser with RF linewidth reduction below instrument limits (1 kHz) and integrated timing jitter values below 300 fs. Dual-tone injection allowed slave laser repetition rate control over a 25 MHz range with reduction of all modal optical linewidths to the master source linewidth, demonstrating phase-locking of all slave modes and coherence improvement.

Stabilization of a passively mode-locked laser by continuous wave optical injection

We investigate numerically and experimentally the properties of a passively mode locked quantum dot semiconductor laser under the influence of cw optical injection. We demonstrate that the waveform instability at high pumping for these devices can be overcome when one mode of the device is locked to the injected master laser and additionally show spectral narrowing and tunability. Experimental and numerical analyses demonstrate that the stable locking boundaries are similar to these obtained for optical injection in CW lasers. © 2010 American Institute of Physics.

Tunable master-oscillator power-amplifier based on chirped quantum-dot structures

A broadly tunable master-oscillator power-amplifier (MOPA) picosecond optical pulse source is demonstrated, consisting of an external cavity passively mode-locked laser diode with a tapered semiconductor amplifier. By employing chirped quantum-dot structures on both the oscillator's gain chip and amplifier, a wide tunability range between 1187 and 1283 nm is achieved. Under mode-locked operation, the highest output peak power of 4.39 W is achieved from the MOPA, corresponding to a peak power spectral density of 31.4 dBm/nm. © 1989-2012 IEEE.

Blue-to-red tunable SHG from a diode-pumped PPKTP waveguide

Summary form only given. Broadly tunable compact visible laser sources in the spectral region of 500-650 nm are valuable in biophotonics, photomedicine and for many applications including spectroscopy, laser projection and confocal microscopy. Unfortunately, commercially available lasers of this spectral range are in practice bulky and inconvenient in use. An attractive method for the realization of portable visible laser sources is the frequency-doubling of the infrared laser diodes in a nonlinear crystal containing a waveguide [1]. Nonlinear crystal waveguides that offer an order-of-magnitude increase in the IR-to-visible conversion efficiency also enable a very different approach to second-harmonic generation (SHG) tunability in periodically-poled crystals, promising order-of-magnitude increase of wavelength range for SHG conversion. This is possible by utilization of a significant difference in the effective refractive indices of the high-order and low-order modes in multimode waveguides [2]. The recent availability of low-cost, good quality semiconductor diode lasers, offering the coverage of a broad spectral range between 1 µ?? and 1.3 µp? [3,4], in combination with well-established techniques to fabricate good quality waveguides in nonlinear crystals, allows compact tunable CW laser sources in the visible spectral region to be realized [2].

Broadly tunable CW green-to-red laser source based on frequency doubling of a quantum-dot external cavity diode laser in a PPKTP waveguide

Here we present a compact tunable all-room-temperature frequency-doubling scheme, using a periodically poled potassium titanyl phosphate (PPKTP) waveguide and a QD-ECDL. A broad wavelength tunability of the second harmonic generated light (SHG) in the spectral region between 567.7 and 629.1 nm was achieved, with maximum conversion efficiencies in range of 0.34%-7.9%. The maximum output power for the SHG light was 4.11 mW at 591.5 nm, achieved for 52 mW of launched pump power at 1183 nm, resulting in a conversion efficiency of 7.9%.

Tunable master-oscillator power-amplifier using all chirped quantum-dot structures

A tunable master-oscillator power-amplifier (MOPA) picosecond optical pulse source using all chirped quantum dot (QD) structures is demonstrated (60nm tunability). Under fundamental mode-locked operation, the highest peak power of 4.39 W is achieved.

Green-to-red tunable SHG of a quantum-dot laser in a PPKTP waveguide

Quasi-phase-matching is an important and widelyused technique in nonlinear optics enabling efficient frequency up-conversion. However, since its introduction almost half a century ago, this technique is well developed for near infrared (IR) but is intrinsically limited in spectral tunability in the visible range by the strict conditions set by the spatial modulation which compensates the momentum mismatch imposed by the dispersion. Here, we provide a fundamental generalization of quasi-phase-matching based on the utilization of a significant difference in the effective refractive indices of the high- and low-order modes in multimode waveguides. This concept enables to match the period of poling in a very broad wavelength range and opens up a new avenue for an order-ofmagnitude increase in wavelength range for frequency conversion from a single crystal. Using this approach, we demonstrate an all-room-temperature continuous-wave (CW) second harmonic generation (SHG) with over 60 nm tunability from green to red in a periodically-poled potassium titanyl phosphate (PPKTP) waveguide pumped by a single broadly-tunable quantumdot laser diode. © 2012 by Astro, Ltd.

High-power versatile picosecond pulse generation from mode-locked quantum-dot laser diodes

This paper presents the current status of our research in mode-locked quantum-dot edge-emitting laser diodes, particularly highlighting the recent progress in spectral and temporal versatility of both monolithic and external-cavity laser configurations. Spectral versatility is demonstrated through broadband tunability and novel mode-locking regimes that involve distinct spectral bands, such as dual-wavelength mode-locking, and robust high-power wavelength bistability. Broad tunability of the pulse repetition rate is also demonstrated for an external-cavity mode-locked quantum-dot laser, revealing a nearly constant pulse peak power at different pulse repetition rates. High-energy and low-noise pulse generations are demonstrated for low-pulse repetition rates. These recent advances confirm the potential of quantum-dot lasers as versatile, compact, and low-cost sources of ultrashort pulses. © 2011 IEEE.

Broadly tunable high-power InAs/GaAs quantum-dot external cavity diode lasers

A record broadly tunable high-power external cavity InAs/GaAs quantum-dot diode laser with a tuning range of 202 nm (1122 nm-1324 nm) is demonstrated. A maximum output power of 480 mW and a side-mode suppression ratio greater than 45 dB are achieved in the central part of the tuning range. We exploit a number of strategies for enhancing the tuning range of external cavity quantum-dot lasers. Different waveguide designs, laser configurations and operation conditions (pump current and temperature) are investigated for optimization of output power and tunability. (C) 2010 Optical Society of America