Room-temperature Continuous-wave Lasing Research Articles

Yellow laser performance of Dy³⁺ in co-doped Dy,Tb:LiLuF₄.

We present laser results obtained from a Dy³⁺-Tb³⁺ co-doped LiLuF₄ crystal, pumped by a blue emitting InGaN laser diode, aiming for generation of a compact 578 nm source. We exploit the yellow Dy³⁺ transition ⁴F(9/2)⇒⁶H(13/2) to generate yellow laser emission. The lifetime of the lower laser level is quenched, via energy transfer, to co-doped Tb³⁺ ions in the fluoride crystal. We report the growth technique, spectroscopic study, and room temperature continuous wave laser results in a hemispherical cavity at 574 nm, and with a highly reflective output coupler at 578 nm. A yellow laser at 578 nm is very relevant for metrological applications, in particular for pumping of the forbidden ¹S₀-³P₀ ytterbium clock transition, which is recommended as a secondary representation of the second in the international system of units.

Room temperature continuous-wave laser performance of LD pumped Er:Lu₂O₃ and Er:Y₂O₃ ceramic at 2.7 μm.

We report the demonstration of continue wave operation of diode end-pumped Er:Y2O3 and Er:Lu2O3 ceramic lasers operating at 2.7 μm at room temperature. The maximum output power of 320 mW and 611 mW was obtained from the Er:Y2O3 and Er:Lu2O3 ceramic lasers, with slope efficiency of 6.5% and 7.6%, respectively. Characteristics of Red-shift in lasing wavelength of the ceramic lasers was investigated and discussed. The study indicates that under 967 nm and 976 nm LD pumping, 15 at.% Er-doped Lu2O3 ceramic exhibit a better performance than that of Y2O3 at room temperature.

Room temperature continuous wave lasing of electrically injected GaN-based vertical cavity surface emitting lasers

Continuous wave (CW) lasing of electrically injected GaN-based vertical cavity surface emitting lasers (VCSELs) was achieved at room temperature. First, a high quality factor (Q) VCSEL-structured device with very narrow linewidth of 0.12 nm, corresponding to a Q-value of 3570 was obtained through two-step substrate transfer technique. However, poor heat dissipation ability prevented the device from lasing. Based on the high-Q resonant cavity design, we further fabricated vertical-structured VCSELs through metal bonding technique on Si substrate. CW lasing from vertical-structured VCSELs was observed with threshold current of density of 1.2 kA/cm2 and lasing linewidth of about 0.20 nm.

Crystal growth, optical spectroscopy, and continuous-wave laser operation of co-doped (Ho,Tm):KLu(WO_4)_2 monoclinic crystals

We report on the crystal growth, optical spectroscopy, and room-temperature continuous-wave laser generation around 2 μm with co-doped (Ho,Tm):KLu(WO4)2 monoclinic crystals. Co-doped crystals at different doping levels were grown by the top-seeded solution growth slow-cooling method. We characterized the spectroscopy of Ho and Tm ions in KLuW in terms of polarized optical absorption, photoluminescence, and lifetime measurements. Continuous-wave laser operation at room-temperature at a wavelength of 2.06 μm was achieved with several crystals at different co-doping levels, establishing that the optimum doping ratio is 5.29×1019 at./cm3 for Ho and 3.10×1020 at./cm3 for Tm (0.5 at. %Ho, 5.0 at. %Tm:KLuW), reaching a maximum output power of 145 mW and a slope efficiency of 12.9%.

Diode-pumped continuous-wave laser operation of co-doped (Ho,Tm):KLu(WO4)2 monoclinic crystal

We report on room-temperature continuous-wave laser operation at 2.06 µm in co-doped (0.5 at% Ho, 5.0 at% Tm):KLu(WO 4 ) 2 monoclinic crystal pumped at 805 nm by a commercially available AlGaAs diode laser stack. A maximum output power of 93 mW and a slope efficiency of 14.7% with respect to absorbed power were achieved. • We achieved on room-temperature continuous-wave laser operation at 2.06 µm. • We studied laser operation in (0.5 at% Ho,5.0 at% Tm):KLu(WO 4 ) 2 monoclinic crystal • We achieved a maximum output power of 93 mW and a slope efficiency of 14.7%.

Design and Characterization of AlGaInAs/InP Buried Heterostructure Transistor Lasers Emitting at 1.3-μm Wavelength

We discuss the wafer design and fabrication process for the 1.3-μm-wavelength AlGaInAs/InP transistor lasers, and the structural dependence of lasing and the electrical characteristics are shown. We particularly focus on the base structure, and the thickness and width dependence are numerically and experimentally analyzed. A thicker base layer resulted in lower optical confinement factor in the quantum wells (QWs), higher optical loss, and lower current gain. In addition, a wider base width caused leak current recombination outside the QWs. By modifying the structure of an n-p-n TL, it was possible to simultaneously realize room-temperature continuous-wave lasing and transistor operation.

In-band pumped Ho^3+:KY_3F_10 2 μm laser

We report the first observation to our knowledge of room-temperature continuous-wave laser operation on the (5)I(7)→(5)I(8) transition of Ho(3+) ions in a KY(3)F(10) single crystal. Using a Tm-doped silica fiber laser operating at 1938 nm as a pump source, a maximum laser power of 1.8 W was obtained at a wavelength of ~2040 nm for 27 W of absorbed pump power with a slope efficiency of 19.1% with respect to absorbed power. At low cavity output coupling, the lasing wavelength shifted to 2060.5 nm. The beam propagation factor (M(2)) was measured to be <1.06 at the maximum output power, confirming fundamental transverse-mode (TEM(00)) operation. Performing a Caird analysis, we determined resonator round-trip losses and intrinsic slope efficiency of 30% and 43.8%, respectively.

Red and orange Pr^3+:LiYF_4 planar waveguide laser

In this Letter we report on room temperature continuous wave laser operation in the red (639 nm, (3)P(0)→(3)F(2)) and orange (604 nm, (3)P(0)→(3)H(6)) spectral regions of Pr(3+)-doped LiYF(4) planar waveguides fabricated by liquid phase epitaxy. Output powers of 25 and 12 mW and slope efficiencies of 5% and 6% were achieved at 639 and 604 nm, respectively, by pumping with an optically pumped semiconductor laser operating at 479.2 nm.

Catalyst-free growth of amorphous silicon nanowires by laser ablation

Amorphous silicon nanowires (NWs), 3–50 nm thick and up to 4 μm long, were grown by room-temperature continuous wave laser ablation of Si in high-pressure (0.1–0.9 MPa) Ar gas without the addition of any catalysts. The diameter and length of the NWs increased as the pressures of the ambient Ar increased. Sphere-like Si particles with diameters of 4–110 nm were observed at the tips of grown NWs and their diameters exhibited a strong correlation with the NW diameters. We propose a stress-driven self-catalytic vapor-liquid-solid mechanism to explain the growth of the NWs.

Efficient continuous-wave laser operation at 1064 nm in Nd:YVO4 cladding waveguides produced by femtosecond laser inscription

Cladding waveguides have been produced in Nd:YVO4 crystals by using femtosecond laser inscription. Such structures are fabricated with circular cross sections and diameters of ~100-120 μm, supporting multi-mode guidance in the two orthogonal polarizations. At room temperature continuous wave laser oscillations at wavelength of ~1064 nm have been realized through the optical pump at 808 nm with slope efficiency as high as 65% and a maximum output power of 335 mW.

Ridge waveguide lasers in Nd:GGG crystals produced by swift carbon ion irradiation and femtosecond laser ablation

We report on the fabrication of ridge waveguide in Nd:GGG crystal by using swift C(5+) ion irradiation and femtosecond laser ablation. At room temperature continuous wave laser oscillation at wavelength of ~1063 nm has been realized through the optical pump at 808 nm with a slope efficiency of 41.8% and the pump threshold is 71.6 mW.

2.7-$\mu{\rm m}$ Single-Frequency ${\rm TEM}_{00}$ Low-Threshold Sb-Based Diode-Pumped External-Cavity VCSEL

We present the design, technology, and performances of a tunable Sb-based diode-pumped type-I quantum-well (QW) vertical-external-cavity surface-emitting lasers emitting at 2.7 μm. The half vertical-cavity surface-emitting laser (VCSEL) structure was grown by molecular beam epitaxy with quantum-well growth temperature of 440 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C. The sample was thermally annealed to optimize the QW gain design. We report on room-temperature continuous-wave laser with 0.17-mW output power and low threshold incident pump intensity of 0.7 kW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> while pumping at 830 nm with a commercial diode laser. The external cavity provides a circular TEM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">00</sub> beam with a low divergence of 3.6 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> . The short mm-long optical cavity laser exhibits tunable single frequency operation, with a sidemode suppression ratio >;>; 23dB, a linewidth <;<;4;GHz, and a linear light polarization. Thermal and optical properties are studied.

Room-temperature continuous-wave operation of lateral current injection wavelength-scale embedded active-region photonic-crystal laser

We have developed a wavelength-scale embedded active-region photonic-crystal laser using lateral p-i-n structure. Zn diffusion and Si ion implantation are used for p- and n-type doping. Room-temperature continuous-wave lasing behavior is clearly observed from the injection current dependence of the output power, 3dB-bandwidth of the peak, and lasing wavelength. The threshold current is 390 μA and the estimated effective threshold current is 9.4 μA. The output power in output waveguide is 1.82 μW for a 2.0-mA current injection. These results indicate that the embedded active-region structure effectively reduce the thermal resistance. Ultrasmall electrically driven lasers are an important step towards on-chip photonic network applications.

Room-temperature continuous wave lasing in deep-subwavelength metallic cavities under electrical injection

Plasmonic nanolasers and spasers continue to attract a great deal of interest from the physics and nanophotonics community, with the experimental observation of lasing as a focus of research. We report the observation of continuous wave lasing in metallic cavities of deep subwavelength sizes under electrical injection, operating at room temperature. The volume of the nanolaser is as small as 0.42\ensuremath{\lambda}${}^{3}$, where \ensuremath{\lambda} $=$ 1.55 \ensuremath{\mu}m is the lasing wavelength. This demonstration will help answer the question of how small a nanolaser can be made, and will likely stimulate a wide range of fundamental studies in basic laser physics and quantum optics on truly subwavelength scales. In addition, such nanolasers may lead to many potential applications, such as on-chip integrated photonic systems for communication, computing, and detection.

Room Temperature CW Operation of Short Wavelength Quantum Cascade Lasers Made of Strain Balanced Ga $_{\bm x}$In$_{\bm {1-x}}$As/Al$_{\bm y}$ In$_{\bm {1-y}}$As Material on InP Substrates

We present our recent development of short wavelength quantum cascade lasers (QCLs) made of strain balanced GaxIn1-xAs/AlyIn1-yAs material on InP substrates. We demonstrate room temperature continuous-wave (CW) lasing of the fundamental lateral mode at four wavelengths of 4.6, 4.0, 3.8, and 3.5 μm. We obtained 60-mW CW output power at 10 °C and 3.55-μm wavelength, which is the shortest CW lasing wavelength demonstrated at room temperature by a QCL, to the best of our knowledge. We also performed a life test on λ = 4.6 μm QCL chips. To date, we have accumulated the life test data for more than 11 000 and 4100 h under two aging conditions, 20°C and 0.85-A constant current, and 60°C and 1-A constant current, respectively.

Continuous Wave Laser Generation in Proton Implanted Nd:GGG Planar Waveguides

We report on room temperature continuous wave laser generation at ~1062 nm from proton implanted Nd:GGG planar waveguides. Single-mode stable laser operation is realized with an 808-nm pump source, resulting in a laser threshold of ~49.3 mW and slope efficiency of 30%. The maximum output power of ~21.9 mW, an absorbed pump power of ~117.4 mW, leads to an optical-to-optical conversion efficiency of 18.7%.

Efficient growth of multi-walled carbon nanotubes by continuous-wave laser vaporization of graphite containing B 4C

Multi-walled carbon nanotubes (MWCNTs), 7–70 nm thick and up to 30 μm long, were efficiently grown by room-temperature continuous-wave laser vaporization of a graphite target containing B 4C in an ambient Ar gas. Adjusting the boron content in the target and Ar gas pressure resulted in a maximum fraction of ∼60% of MWCNTs in the deposits. The straightness of the MWCNTs and graphene layers with an interlayer spacing of ∼0.35 nm indicated that the degree of graphitization was fairly high in the grown MWCNTs. However, the features of D, G, and 2D bands in the Raman spectrum of a deposit suggested boron doping in the MWCNTs. An apparent Young’s modulus of a grown MWCNT was measured to be 0.68 TPa and comparable to those of heat-treated vapor grown carbon nanofibers. MWCNTs are thought to grow on molten boron carbide particles acting as seeds at high temperatures of up to ∼2400 °C.

Room-temperature continuous wave laser oscillations in Nd:YAG ceramic waveguides produced by carbon ion implantation

We report on the generation of continuous wave lasers at a wavelength of ∼1064 nm in a Nd:YAG ceramic waveguide at room temperature. The waveguide was fabricated by using 6 MeV carbon ion implantation at a fluence of 3×1014 ions/cm2. Laser operation has been realized with a slope efficiency as high as ∼11%. The pump threshold of an 808-nm laser beam for the waveguide laser oscillation is 19.5 mW.

Near room temperature continuous-wave laser operation from type-I interband transitions at wavelengths beyond 4 μm

Nonradiative Auger recombination has limited room temperature continuous-wave (cw) operation of type-I interband lasers to wavelengths shorter than 3.36 μm. Using IV–VI semiconductor quantum well microdisk structures, near room temperature laser operation at longer wavelengths is achieved. Their active region consists of type-I single quantum wells of PbSe embedded in PbSrSe barriers. Under optical excitation, single mode cw emission at 4.3 μm is demonstrated up to 2 °C. This proves the feasibility of cw-operation of long wavelength interband lasers up to room temperature.

Long rectangle resonator 1550 nm AlGaInAs/InP lasers

1550 nm AlGaInAs/InP long rectangle resonator lasers with three sides surrounded by SiO2 and p electrode layers are fabricated by planar technology, and room-temperature continuous-wave lasing is realized for a laser with a length of 53 μm and a width of 2 μm. Multiple peaks with wavelength intervals of Fabry-Pérot mode intervals and mode Q factors of about 400 and a lasing mode with a Q factor over 8000 are observed from the lasing spectrum at threshold current. The numerical results of the FDTD simulation indicate that the lasing mode may be a whispering-gallery mode, which is a coupled mode of two high-order transverse modes of the waveguide.