Low Threshold CW Research Articles

Low-threshold CW eye-safe vortex generation from an intracavity pump-wave off-axis pumped OPO.

A low-threshold efficient setup for CW wavelength versatile vortex generation is proposed. The intracavity optical parametric oscillator is utilized for low-threshold operation. By using the pump-wave off-axis pumping for the signal-wave oscillator, high-order Hermite-Gaussian modes at the eye-safe region can be obtained, which can further generate a vortex via an astigmatism mode converter. The overall laser performance is additionally verified to be better by comparing it with the diode off-axis pumping method where the TEM1,0 pump wave was generated first for the signal-wave TEM1,0 mode oscillation. This method is expected to be further applied for more complicated structured light generation.

Low-threshold dual-wavelength CW mid-IR laser from shared intracavity quasi-phase-matched OPO.

A low-threshold continuous wave dual-wavelength mid-infrared laser is demonstrated by using an intracavity optical parametric oscillator (OPO) with a dual-wavelength pump wave. To realize a high-quality dual-wavelength pump wave, a composite Nd:YVO4/Nd:GdVO4 gain medium is applied for a linear polarized state and synchronization output. With the quasi-phase-matching OPO process, it is found that the dual-wavelength pump wave shares equal signal wave oscillation and leads to a lower OPO threshold. Finally, a diode threshold pumped power of barely 2 W can be achieved for the balanced intensity dual-wavelength watt-level mid-IR laser.

Design of a Monolithic Low-Threshold Narrow-Linewidth CW Mid-IR Silicon Raman Laser

We present the design and anticipated performance of an optically pumped monolithic all-silicon mid-IR (MIR) Raman laser. For the proposed 3.15 um cw laser design pumped at a 2.71 um pump wavelength, we estimate a threshold pump power of < 10 mW and an estimated output laser linewidth of <50 MHz. This design may pave the road toward demonstration of the first mid-IR silicon Raman laser.

Low threshold 1260nm (GaIn) (NAs) semiconductor disk laser

Low threshold cw laser emission from a semiconductor disk laser emitting at 1260nm was demonstrated. Using high quality metal-organic vapor phase epitaxy (GaIn) (NAs) material, nonradiative processes could be minimized. As a consequence, threshold pump power densities have been reduced down to 5kW∕cm2. The capture efficiency of carriers into the quantum wells was found to be uncritical.

1.5 µm vertical-cavity surface-emitting lasersutilising low loss Al x O y /GaAs mirrors

Low threshold power vertical-cavity surface-emitting lasers are fabricated by using low loss AlxOy/GaAs mirrors as output couplers. A 5 µm-aperture laser with a low threshold CW pump power of 1.4 mW at room temperature and a 16 µm-aperture laser operating in CW mode up to 64°C are produced.

Low-threshold room-temperature CW operation of ZnSe-basedblue/green laser diodes grown on conductive ZnSe substrates

SCH laser structures of ZnCdSe/ZnSe/ZnMgSSe have been grown on conductive ZnSe substrates by molecular beam epitaxy. Continuous-wave laser operation at room temperature was observed at a wavelength of 527.9 nm (2.349 eV). The threshold current and threshold voltage were 44 mA (222 A/cm/sup 2/) and 5.4 V, respectively. A lifetime of 74 s at a constant light output power of 2 mW was obtained.

Very low threshold and high power CW operation in1.55 µm gain-coupled DFB lasers with periodically etched quantum wells

The authors demonstrate extremely low threshold and high CW output power in 1.55 µm gain coupled DFB lasers. The structure is an MQW strain compensated active layer with first-order grating etched on the upper wells. The lowest thresholds of 2.5 mA at 20°C and 10 mA at 80°C are obtained using one HR facet coating. With an AR front facet, the CW output is increased up to 40 mW, while the threshold current remains < 10 mA.

Low threshold CW operation ofGaInP/AlGaInP DFB lasers at 680 nm

Continuous wave operation of GaInP/AlGaInP DFB lasers at room temperature is reported. The DFB lasers in ridge waveguide geometry show stable singlemode emission with a sidemode suppression > 30 dB and a threshold current of 25.9 mA at 20°C. Singlemode operation could be achieved for a large temperature range between –10 and 40°C. Even for 40°C the threshold current remains below 50 mA.

Circular-grating surface-emitting distributed Bragg reflector lasers on an InGaAs-GaAs structure for 0.48-μm applications

In this paper, we report on the design and fabrication of electrically-pumped circular-grating surface-emitting DBR lasers for operation in the 0.98-/spl mu/m wavelength range. The layer structure with InGaAs-GaAs-AlGaAs strained multiquantum-wells was obtained by one-step epitaxial growth. Circular gratings are defined by electron-beam lithography around circular gain sections of different diameters. Low threshold CW operation as low as 26 mA for a 60-/spl mu/m diameter gain section, and high-power pulsed operation of over 120 mW for a 100-/spl mu/m diameter gain region are demonstrated. A quasi-circular far-field pattern with a divergence of about 1/spl deg/ is obtained.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Low threshold CW operation of circular-grating surface-emitting DBR lasers using MQW and a self-aligned process

In this letter, we present the first room temperature continuous wave operation of circular-grating surface-emitting DBR lasers. The structure is an InGaAs/GaAs strained multiquantum-well. A modified fabrication process with a better control on the steps is used. A CW threshold current as low as 26 mA at a lasing wavelength of about 977 mm are reported. This is the first demonstration of CW operation for these lasers in any material system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Broad-range wavelength-tunable superstructure grating (SSG) DBR lasers

A broad tuning range is demonstrated in tunable DBR lasers with a novel superstructure grating (SSG). These SSG reflectors were fabricated by electron-beam lithography, and grating performance was evaluated by measuring the transmittance characteristics of a ridge-type SSG reflector. Incorporating this SSG reflector into distributed-Bragg-reflector (DBR) laser results in lasers that can be tuned over a wide wavelength range by using coarse and fine tuning mechanisms. Wavelength-tunable SSG DBR lasers were fabricated and operated under low-threshold CW conditions. Wavelength tuning ranges of 50 and 100 nm were designed and experimentally measured to be 50 and 83 nm, respectively, with single-mode operation. >

Low-threshold CW operation of square-shaped semiconductor ring lasers (orbiter lasers)

The CW operation of square-shaped semiconductor ring lasers is demonstrated with a threshold current as low as 6 mA. The ring resonator consists of straight waveguides and four total reflection mirrors. The lasers are fabricated using Br/sub 2/ dry etching on an InGaAs/GaAs strained single-quantum-well graded-index separate-confinement heterostructure wafer. The low-threshold CW operation is due to the high differential gain of the wafer and the low-loss total reflection mirror.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Low-threshold (≤ 92 A/cm2) 1.6 μm strained-layer single quantum well laser diodes optically pumped by a 0.8 μm laser diode

To explore the ultimate threshold current limit in long-wavelength semiconductor lasers, InxGa1−xAs/InP strained-layer single quantum well laser diodes were studied for the first time by optically pumping with a 0.8 μm laser diode. Low-threshold (≤92 A/cm2) cw operation was obtained and the lasing wavelength (1.62 μm) corresponding to the transition from the first quantization state of a 25 Å In0.8Ga0.2As well was observed. By taking the carrier collection efficiency (≤77%) into account, the actual threshold current density could be as low as 70 A/cm2.

Low-threshold CW operation of an erbium-doped fibre laser pumped at 807 nm wavelength

We report an erbium-doped fibre laser operating CW at a wavelength of 1555nm pumped at a wavelength of 807 nm, with a threshold launched pump power of 2.5 mW. This level corresponds to only 1 mW of pump power absorbed.

Miniature CW and active internally Q-switched Nd:MgO:LiNbO&amp;lt;inf&amp;gt;3&amp;lt;/inf&amp;gt;lasers

We report a 10 mW threshold miniature device in which internal <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> -switching of a single Nd:MgO:LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> crystal is achieved. Pulsewidths of 30 ns have been observed. Peak powers of 5 W have been attained with less than 60 mW of 598 nm pump power and with less than 1 percent output coupling. The switching voltage is lower than 300 V. The consequences of the elastooptic effect and the photoconductivity on device performance are investigated. A highly efficient CW laser and a low threshold CW laser made of the same material are also reported. Photorefractive damage due to the photovoltaic effect is found to be almost nonexistent in these lasers when pumped in the near-infrared.

Low-threshold tunable CW and Q -switched fibre laser operating at 1.55 μm

A new single-mode fibre laser source is described. The laser is tunable over 25 nm in the wavelength region of 1.55 μm and produces in excess of 2 W peak power in a Q-switched mode.

Tunable CW laser oscillation of NdP5O14 at 1.3 ?m

Low-threshold tunable cw laser oscillation is achieved at the4 F 3/2→4 I 13/2 transition of NdP5O14. Continuous tunign over 1.8% of the central wavelenght is possible with 55 mW of absorbed pump power. At gain line maximum near 1.32 μ, the output power exceeded 1 mW. Pump threshold as low as 8 mW was observed. Reliable cw operation of the 1.3 μm NdP5O14 laser pumped by a 15 mW AlGaAs laser diode is demonstrated.

Low Threshold CW Operation GaInAsP/InP Mushroom Stripe Laser (MSL) Emitting at 1.27 µm

Low Threshold CW Operation GaInAsP/InP Mushroom Stripe Laser (MSL) Emitting at 1.27 µm

Low threshold cw laser operation of Nd:YLF

Low threshold cw laser operation of Nd:YLF

Low threshold CW room temperature laser operation of Nd:CAMGAR at 0.941 &amp;#181;m

Low threshold CW room temperature laser operation of Nd:CAMGAR at 0.941 &amp;#181;m