Green Output Research Articles

Continuous-wave Nd:GdVO4/LBO laser at 541.5 nm under diode pumping into the emitting level

We report a green laser at 541.5 nm generation by intracavity frequency doubling of a continuous wave (cw) laser operation of a 1083 nm Nd:GdVO4 laser under 880 nm diode pumping into the emitting level 4 F 3/2. A LiB3O5 (LBO) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 17.8 W, as high as 2.52 W of cw output power at 541.5 nm is achieved. The optical-to-optical conversion efficiency is up to 14.2%, and the fluctuation of the green output power was better than 3.6% in the given 30 min.

Diode-pumped Nd:GAGG-LBO laser at 531 nm

We report a green laser at 531 nm generation by intracavity frequency doubling of a continuous wave (cw) laser operation of a 1062 nm Nd:GAGG laser under in-band diode pumping at 808 nm. A LiB3O5 (LBO) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 18.5 W, as high as 933 mW of cw output power at 531 nm is achieved. The fluctuation of the green output power was better than 3.5% in the given 4 h.

The 'Green' concern in e-learning development findings from a university case study in the UK

Purpose : the paper tries to address the question of whether universities concern ‘Green’ during e-learning development. Methodology : a case study approach is chosen for establishing empirical evidence and describing the phenomenon. Findings : the paper found that the green concern did not appear at the initial stage of e-learning strategy although there is green output – reusable resource at the e-learning delivery stage. However, the diversity of cost is still a critical concern for the e-learning adoption. Originality/value : this paper shows the missing awareness of green concern in the e-learning development process, especially in the e-learning strategy.

All-solid-state intracavity frequency-doubled Nd:Y0.36Gd0.64VO4-GdCa4O(BO3)3 green laser under direct 880 nm pumping

We report a green laser at 532 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1064 nm Nd:Y0.36Gd0.64VO4 laser under in-band diode pumping at 880 nm. An GdCa4O(BO3)3 (GdCOB) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 17.8 W, as high as 2.92 W of CW output power at 532 nm is achieved. The optical-to-optical conversion efficiency is up to 16.4%, and the fluctuation of the green output power was better than 2.5% in the given 30 min.

Power output and efficiency of quantum dot attached to ferromagnetic electrodes with non-collinear magnetic moments

Non-linear charge and heat transport through a single-level quantum dot in the Coulomb blockade regime is investigated within the framework of non-equilibrium Green function formalism and power output and efficiency of the device are studied. It is found that maximum power as well as efficiency depends on the relative orientation of magnetic moments in electrodes and can vary with polarization factor p. In general, power output is suppressed in magnetic systems and decreases with polarization. The highest efficiency can be attained in antiparallel configuration, and moreover, it does not depend on p. Spin power as well as spin efficiency of the system is introduced and discussed. It is also shown that in the Coulomb blockade regime the (spin) efficiency of the device operating under maximum power conditions varies with temperature bias in a non-monotonic way and shows a flat maximum for low ΔT.

Linear electromagnetic devices for vibration damping and energy harvesting: Modeling and testing

Over the past decades, the research on structural vibration control has mainly focused on ‘energy dissipation’ strategy using various dampers for hazard mitigation. This paper proposes a novel application of linear motion electromagnetic (EM) devices, termed linear EM dampers hereinafter, for both vibration damping and energy harvesting. The kinetic energy caused by earthquakes, wind or traffic loads is not only dissipated by EM dampers, but also stored by energy-harvesting electric circuits connected to EM dampers. The green and regenerative energy output may provide an alternative power supply to portable and wireless devices at remote sites. This paper presents a theoretical and experimental study of linear EM dampers connected with four representative circuits. The dynamic characteristics of linear EM dampers, including parasitic damping, EM damping, energy conversion efficiency and output power, are modeled and discussed systematically in each case. The modeling is further verified by a series of dynamic testing of a small-scale linear EM damper, which is cyclically tested on a MTS machine at different frequencies and amplitudes. A good match between the modeling and testing results clearly demonstrates that the described model can predict the performance of the linear EM damper and energy harvesting circuit very well. The promises and challenges of using EM dampers in future civil infrastructure for both vibration damping and energy harvesting are discussed based on the outcome of this study.

Enhanced luminescence of Tb3+ by efficient energy transfer from Ce3+ in Sr2B5O9Cl host

Ce3+ and Tb3+ co-doped Sr2B5O9Cl phosphors with intense green emission were prepared by the conventional high-temperature solid-state reaction technique. A broad band centered at about 315 nm was found in phosphor Sr2B5O9Cl: Ce3+, Tb3+ excitation spectrum, which was attributed to the 4f-5d transition of Ce3+. The typical sharp line emissions ranging from 450 to 650 nm were originated from the 5D4 → 7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ions. The photoluminescence (PL) intensity of green emission from Tb3+ was enhanced remarkably by co-doping Ce3+ in the Tb3+ solely doped Sr2B5O9Cl phosphor because of the dipole–dipole mechanism resonant energy transfer from Ce3+ to Tb3+ ions. The energy transfer process was investigated in detail. In light of the energy transfer principles, the optimal composition of phosphor with the maximum green light output was established to be Sr1.64Ce0.08Tb0.1Li0.18B5O9Cl by the appropriate adjustment of dopant concentrations. The PL intensity of Tb3+ in the phosphor was enhanced about 40 times than that of the Tb3+ single doped phosphor under the excitation of their optimal excitation wavelengths.

Diode-pumped Yb:GSO-LBO laser at 544 nm

We report a green laser at 544 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1088 nm Yb:GSO laser under in-band diode pumping at 940 nm. An LiB3O5 (LBO) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 17.8 W, as high as 444 mW of CW output power at 544 nm is achieved. The fluctuation of the green output power was better than 4.6% in the given 4 h.

Internal resonantly enhanced frequency doubling of continuous-wave fiber lasers

In this Letter we describe a simple method for frequency doubling in high-power CW fiber lasers that offers the prospect of very high conversion efficiency and high power in the visible wavelength regime. Our approach is based on second harmonic generation in an enhancement resonator within the fiber laser cavity and does not require active cavity length stabilization. This technique has been applied to a cladding-pumped Yb-doped fiber laser to generate 19 W of linearly polarized CW green output at 540 nm, with excellent temporal stability for 90 W of absorbed diode pump power at 975 nm. The prospects for further improvement in performance with respect to conversion efficiency and output power are considered.

Compact passively Q-switched green laser with periodically poled MgO:LiNbO3

Passively Q-switched green output with Cr4+:YAG as saturable absorber and PPMgLN as the frequency doubling crystal was realized in a compact diode end-pumped Nd:YVO4 laser. The green light output power, pulse width, pulse repetition rate, pulse energy and peak power with three Cr4+:YAG of different initial transmissions were investigated. The maximum average output power was 1.2 W at the pump power of 4.0 W and the maximum conversion efficiency was 30% with the Cr4+:YAG of 90% initial transmission. The maximum pulse energy and minimum pulse width were 10.9 μJ and 12 ns with the Cr4+:YAG of 75% initial transmission.

Efficient green-light generation by proton-exchanged periodically poled MgO:LiNbO_3 ridge waveguide

Efficient cw 532 nm green-light generation is demonstrated using a periodically poled MgO:LiNbO3 ridge waveguide prepared by a process that combines annealed proton exchange and precise dicing. Performance of waveguides with different widths has been investigated. The 6-μm-wide, 1.6-cm-long uncoated ridge waveguide has achieved a green output power of 127 mW under a coupled fundamental light power of 250 mW. The highest conversion efficiency achieved is 53%.

A 10 W Diode-Pumped Solid-State Green Laser

This paper reports a 10W solid state green laser TEM00 mode output operation, pumped by 3 x 40W LD arrays. The theoretical analysis of the cavity stability and operation mode selection are presented. To make the system more compact, a Brewster plate is specially designed to function both as a polariser as well as a green output coupler.In the experiment, we obtain maximum 10W green laser TEM00 output at 10kHz by establishing a concave-flat stable resonator. Angle mismatch in the frequency doubling is corrected by optimising the crystal temperature to maximise the laser output. The system is completely enclosed in a customised chassis, enabling further integration of scanner head for application testings as well as inhibiting environmental factors that will affect the performance of the laser.

Multicrystal, continuous-wave, single-pass second-harmonic generation with 56% efficiency

We report a simple and compact implementation for single-pass second-harmonic-generation (SP-SHG) of cw laser radiation, based on a cascaded multicrystal (MC) scheme, that can provide the highest conversion efficiency at any given fundamental power. By deploying a suitable number of identical 30-mm-long MgO:sPPLT crystals in a cascade and a 30W cw Yb-fiber laser at 1064nm as the fundamental source, we demonstrate SP-SHG into the green with a conversion efficiency as high as 56% in the low-power as well as the high-power regime, providing 5.6W of green output for 10W and 13W of green output for 25.1W of input pump power. The MC scheme permits substantial increase in cw SP-SHG efficiency compared to the conventional single-crystal scheme without compromising performance with regard to power stability and beam quality.

Green laser sources optimized for highly efficient microdisplay‐based field‐sequential mobile projectors

Abstract— A novel green laser source, based on a monolithic cavity microchip laser platform, has been developed. The laser is designed to be a part of a miniature and efficient RGB light source for microdisplay‐based mobile projector devices. The use of highly efficient, periodically poled MgO‐doped lithium niobate as the non‐linear frequency doubler allows for a significant increase in the overall efficiency of the green microchip laser. Specifically, a 50–150‐mW green output with a wall‐plug efficiency exceeding 10% in the temperature range of greater than 40°C has been demonstrated. A compact package for this laser source with a volume less than 0.33 cm3 is discussed and results of performance tests are presented.

A simple, compact, and efficient diode-side-pumped linear intracavity frequency doubled Nd:YAG rod laser with 50 ns pulse width and 124 W green output power

We have developed an efficient and high power repetitively Q-switched diode-pumped intracavity frequency doubled Nd:YAG/LiB(3)O(5) based green laser capable of generating 124 W of average green power with 50 ns pulse duration in a highly compact and robust linear cavity configuration. The pump to green beam conversion efficiency is 16.8% and the overall wall-plug efficiency is 8.3%. The long term power stability is excellent with +/-0.4 W variation at the maximum output power and +/-2% amplitude fluctuation with +/-2.9 ns timing jitter. The M(2) parameter of the green beam was measured to be approximately 27. This, combined with the short pulse duration and the high average power, makes this laser ideal for pumping ultrafast Ti:sapphire laser amplifier systems and for micromachining applications.

Improving microstructural quality of semipolar (112̱2) GaN on m-plane sapphire by a two-step growth process

This letter reports a two-step growth process for improving microstructural quality of semipolar (112̱2) GaN on nitridized m-plane sapphire. The two-step growth of (112̱2) GaN, islanding growth under high pressure followed by islands coalescence under low pressure, went through a roughening-recovery process, which was found very effective in reducing the density of stacking faults and dislocations in (112̱2) GaN. The x-ray rocking curves of both on-axis and off-axis planes were narrowed down by more than 50%. The improvement of GaN quality was confirmed by a boost in blue and green optical output of semipolar (112̱2) InGaN/GaN quantum wells.

Comparative study on the intracavity frequency-doubling 532 nm laser based on gray-tracking-resistant KTP and conventional KTP

A comparative study of a frequency-doubling 532 nm laser based on gray-tracking-resistant KTP (GTR-KTP) and conventional KTP is presented. The intracavity GTR-KTP was proved to have better temperature characteristics than that of conventional KTP. Within the normalized output power variation range of 0.8-1.0, GTR-KTP has a temperature tolerance of 35 degrees C, broader than the 21 degrees C obtained with conventional KTP. Under the laser diode (LD) pump power of 180 W, the maximum average output power at 532 nm was 40.6 W for GTR-KTP at a repetition frequency of 10 kHz. In the case of conventional KTP, the maximum available LD pump power was limited to 150 W, with the corresponding maximum green average output power of 27.2 W.

High-power, single-frequency, continuous-wave second-harmonic-generation of ytterbium fiber laser in PPKTP and MgO:sPPLT

Characteristics of high-power, narrow-linewidth, continuous-wave (cw) green radiation obtained by simple single-pass second-harmonic-generation (SHG) of a cw ytterbium fiber laser at 1064 nm in the nonlinear crystals of PPKTP and MgO:sPPLT are studied and compared. Temperature tuning and SHG power scaling up to nearly 10 W for input fundamental power levels up to 30 W are performed. Various contributions to thermal effects in both crystals, limiting the SHG conversion efficiency, are studied. Optimal focusing conditions and thermal management schemes are investigated to maximize SHG performance in MgO:sPPLT. Stable green output power and high spatial beam quality with M(2)<1.33 and M(2)<1.34 is achieved in MgO:sPPLT and PPKTP, respectively.

20.2: High‐Efficiency Green Laser Source for Compact Projectors

AbstractWe demonstrate a novel green laser source, based on a monolithic cavity microchip laser platform. The use of our highly efficient, Periodically Poled MgO‐doped Lithium Niobate (PPMgOLN) as the frequency doubler allows obtaining a significant increase in the overall efficiency of the green microchip laser. Specifically, we demonstrate 200mW green output and &gt;10% wall‐plug efficiency in the 35°C temperature range.

Stable, 96 W, continuous-wave, single-frequency, fiber-based green source at 532 nm

We present a stable, high-power, cw, single-frequency green source in a compact and practical design based on a simple single-pass second-harmonic generation of a cw ytterbium fiber laser at 1064 nm in MgO-doped periodically poled stoichiometric LiTaO(3). Using a 30-mm-long crystal containing a single grating, we have generated 9.64 W of cw radiation at 532 nm with a fundamental power of 29.5 W at a single-pass conversion efficiency of 32.7%. The output power is naturally stable with a peak-to-peak fluctuation of 7.6% over the first 8 h and 9% over 13 h. Over the entire range of fundamental powers, the generated green output is single frequency with an instantaneous linewidth of 6.5 MHz and frequency stability of <32 MHz over 30 min and has a TEM(00) spatial profile with M(2)<1.33.