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%.

Generation of CW tunable visible light by SHG of QD laser in a PPKTP waveguide

We demonstrate a CW tunable compact all-room-temperature laser system in the visible spectral region from 567.7 nm to 629.1 nm, by frequency doubling in a periodically-poled KTP waveguide crystal using a tunable quantum-dot external-cavity diode laser.

THz emission from quantum dot-based THz antennas pumped by a tunable quantum-dot laser diode

The THz optoelectronics field is now maturing and semiconductor-based THz antenna devices are becoming more widely implemented as analytical tools in spectroscopy and imaging. Photoconductive (PC) THz switches/antennas are driven optically typically using either an ultrashort-pulse laser or an optical signal composed of two simultaneous longitudinal wavelengths which are beat together in the PC material at a THz difference frequency. This allows the generation of (photo)carrier pairs which are then captured over ultrashort timescales usually by defects and trapping sites throughout the active material lattice. Defect-implanted PC materials with relatively high bandgap energy are typically used and many parameters such as carrier mobility and PC gain are greatly compromised. This paper demonstrates the implementation of low bandgap energy InAs quantum dots (QDs) embedded in standard crystalline GaAs as both the PC medium and the ultrafast capture mechanism in a PC THz antenna. This semiconductor structure is grown using standard MBE methods and allows the device to be optically driven efficiently at wavelengths up to ~1.3 µm, in this case by a single tunable dual-mode QD diode laser.

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.

Orange light generation from a PPKTP waveguide end pumped by a cw quantum-dot tunable laser diode

A compact all-room-temperature frequency-doubling scheme generating cw orange light with a periodically poled potassium titanyl phosphate waveguide and a quantum-dot external cavity diode laser is demonstrated. A frequency-doubled power of up to 4.3 mW at the wavelength of 612.9 nm with a conversion efficiency exceeding 10% is reported. Second harmonic wavelength tuning between 612.9 nm and 616.3 nm by changing the temperature of the crystal is also demonstrated. © Springer-Verlag 2010.

Broadly tunable quantum-dot based ultra-short pulse laser system with different diffraction grating orders

A broadly tunable quantum-dot based ultra-short pulse master oscillator power amplifier with different diffraction grating orders as an external-cavity resonance feedback is studied. A broader tuning range, narrower optical spectra as well as higher peak power spectal density (maximun of 1.37 W/nm) from the second-order diffraction beam are achieved compared to those from the first-order diffraction beam in spite of slightly broader pulse duration from the secondorder diffraction. © The Institution of Engineering and Technology 2013.

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.

InAs/AlSb widely tunable external cavity quantum cascade laser around 3.2 μm

Room temperature, tunable, external-cavity short-wavelength InAs/AlSb quantum cascade laser (QCL) is reported. Wavelength tuning of 85 nm for the spectral range between 3190 nm and 3275 nm has been achieved by rotating the diffraction grating forming the external cavity. To suppress lasing inside the QCL cavity, its ridge was tilted by 7° at the external cavity end. The optimal tilting angle of the laser ridge was chosen by careful consideration of the return losses of the TM-polarized waveguide mode from the diffraction grating in a quasi-Littrow configuration and the Fabry-Pérot feedback from the tilted laser facet. No antireflection coating was used. © 2013 American Institute of Physics.

Orange-to-red tunable picosecond pulses by frequency doubling in a diode-pumped PPKTP waveguide

A compact picosecond all-room-temperature orange-to-red tunable laser source in the spectral region between 600 and 627 nm is demonstrated. The tunable radiation is obtained by second-harmonic generation in a periodically poled potassium titanyl phosphate (PPKTP) multimode waveguide using a tunable quantum-dot external-cavity mode-locked laser. The maximum second-harmonic output peak power of 3.91 mW at 613 nm is achieved for 85.94 mW of launched pump peak power at 1226 nm, resulting in conversion efficiency of 4.55%. © 2013 Optical Society of America.

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

Generation of tunable visible picosecond pulses by frequency-doubling of a quantum-dot laser in a PPKTP waveguide

We demonstrate a compact all-room-temperature picosecond laser source broadly tunable in the visible spectral region between 600 nm and 627 nm. The tunable radiation is obtained by frequency-doubling of a tunable quantum-dot external-cavity mode-locked laser in a periodically-poled KTP multimode waveguide. In this case, utilization of a significant difference in the effective refractive indices of the high- and low-order modes enables to match the period of poling in a very broad wavelength range. The maximum achieved second harmonic output peak power is 3.25 mW at 613 nm for 71.43 mW of launched pump peak power at 1226 nm, resulting in conversion efficiency of 4.55%. © 2013 Copyright SPIE.

Effects of crosstalk in WDM optical label switching networks due to wavelength switching of a tunable laser

Crosstalk caused by switching events in fast tunable lasers in an optical label switching (OLS) system is investigated for the first time. A wavelength-division-multiplexed OLS system based on subcarrier multiplexed labels is presented which employs a 40-Gb/s duobinary payload and a 155-Mb/s label on a 40-GHz subcarrier. Degradation in system performance as the transmitters switch between different channels is then characterized in terms of the frequency drift of the tunable laser.

Tunable and multiple-wavelengths/temporal output from gain-switched diode laser and a four Bragg-grating fiber

The spectral narrowing and selective tuning of picosecond pulse outputs from gain-switched diode laser and a four Bragg-grating fiber, were investigated. The fiber used under investigation was designed to provide spectral narrowing and multiple wavelength/temporal output. The maximum transmission out of each of the four output fibers was ∼7.5 mW, for a current of 180 mA. The results show that an output of any combination of multiple wavelengths is only produced at modulation frequencies which satisfy resonant conditions for all cavity arms simultaneously.

Tunable Pt nanocatalysts for the aerobic selox of cinnamyl alcohol

The selective aerobic oxidation of cinnamyl alcohol over Pt nanoparticles has been tuned via the use of mesoporous silica supports to control their dispersion and oxidation state. High area two-dimensional SBA-15, and three-dimensional, interconnected KIT-6 silica significantly enhance Pt dispersion, and thus surface PtO2 concentration, over that achievable via commercial low surface area silica. Selective oxidation activity scales with Pt dispersion in the order KIT-6 ≥ SBA-15 > SiO2, evidencing surface PtO2 as the active site for cinnamyl alcohol selox to cinnamaldehyde. Kinetic mapping has quantified key reaction pathways, and the importance of high O2 partial pressures for cinnamaldehyde production. © 2013 The Royal Society of Chemistry.