Stimulated Emission Wavelength Research Articles

GaN-based blue laser diode with 6.0 W of output power under continuous-wave operation at room temperature

In this work, we reported the room-temperature continuous-wave operation of 6.0 W GaN-based blue laser diode (LD), and its stimulated emission wavelength is around 442 nm. The GaN-based high power blue LD is grown on a c-plane GaN substrate by metal organic chemical vapor deposition (MOCVD), and the width and length of the ridge waveguide structure are 30 and 1200 μm, respectively. The threshold current is about 400 mA, and corresponding threshold current density is 1.1 kA/cm2.

Room-temperature continuous-wave operation of GaN-based blue-violet laser diodes with a lifetime longer than 1000 h

GaN-based continuous-wave operated blue-violet laser diodes (LDs) with long lifetime are demonstrated, which are grown on a c-plane GaN substrate by metal organic chemical vapor deposition with a 10 × 600 μm2 ridge waveguide structure. The electrical and optical characteristics of a blue-violet LD are investigated under direct-current injection at room temperature (25 °C). The stimulated emission wavelength and peak optical power of the LD are around 413 nm and over 600 mW, respectively. In addition, the threshold current density and voltage are as small as 1.46 kA/cm2 and 4.1 V, respectively. Moreover, the lifetime is longer than 1000 hours under room-temperature continuous-wave operation.

Stimulated-emission wavelength switching in optically pumpedInGaAs/AlGaInAs laser heterostructures

We report stimulated near-IR emission in opticallypumped InGaAs/AlGaInAs heterostructures and stimulated-emission wavelength switching from 1.9 to 1.5 and then to1.2 μm with increasing optical pump intensity. The wavelength switching behaviour of the heterostructures depends ontheir geometry (band-gap profile) and the competitionbetween stimulated emissions at different frequencies indifferent parts of the system.

Properties of 1.3 μm InGaNAs laser material grown by MBE using a N 2/Ar RF plasma

InGaNAs single quantum well laser diodes were grown on GaAs substrates using solid-source molecular beam epitaxy with N 2/Ar gas mixtures in an radio-frequency (RF) plasma cell. The structures employ GaNAs barriers which reduce the quantum confinement and extend the room temperature stimulated emission wavelength to 1.36 μm. Test quantum well structures were grown with and without these barriers to demonstrate the significant redshift in emission (∼36 meV) resulting from the change in potential barrier height. We also demonstrate the temperature dependence of post-deposition rapid thermal annealing, and show that the optimal temperature is near 800 °C for both types of test structure. Likewise, the blueshift with annealing is similar in both cases. The broad-area, ridge-waveguide laser diodes exhibit internal quantum efficiencies and internal losses of η i=53±7% and α i=9.8±4.0 cm −1, with a transparency current density of 304±17 A cm −2. These results demonstrate the potential of the N 2/Ar RF plasma technique for device-quality MBE layers.

Mid-infrared InSb and InAlSb diode lasers

Diode lasers with an In0.948Al0.052Sb gain region have been grown by molecular beam epitaxy onto nominally matched InGaSb substrates, and onto mismatched InSb substrates. The former had a stimulated emission wavelength of 3.9 µm at 77 K, with the threshold current density being 140 Acm-2 and maximum operating temperature 165 K. The latter had a stimulated emission wavelength of 3.6 µm at 77 K, with the threshold current density being 417 Acm-2 and maximum operating temperature 160 K.

Red-shift of stimulated emission in ZnSe-based semiconductors

A red-shift in the stimulated emission wavelength with increasing intensity is observed using picosecond laser excitation of molecular-beam-epitaxial ZnSe epilayers and ZnSe-based quantum-well structures. This red-shift occurs across a wide temperature range (4–300 K) and for a wide range of epilayer and quantum-well samples. We show that sample heating is not the origin of this shift. A variety of emission mechanisms are discussed but none provides a complete description of the observed experimental trends.

Possible impact of surface morphology on stimulated emission in GaN–AlGaN double heterostructures

Stimulated emission is studied in a hexagonal AlGaN/GaN/AlGaN double heterostructure grown on a (0 0 0 1) sapphire substrate by low pressure (200 mbar) metallorganic vapor phase epitaxy. A sharp increase in the edge emitted luminescence intensity is obtained above a threshold excitation density of 40 kW/cm 2 and is accompanied by a strong narrowing of the luminescence line width. The specific surface morphology of the heterostructure is suspected to be responsible for an optical feedback in the sample. Although the surface is extremely smooth yielding roughness values of σ RMS<0.36 nm an almost perfectly periodic corrugation is superimposed reflecting the columnar growth mode of the nitrides. The measured quasi-periodic corrugation of λ=110–120 nm periodicity perfectly matches the stimulated emission wavelength in the dielectric material.

Excited state absorption and laser potential of Mn 5+-doped Li 3PO 4

Excited state absorption (ESA) spectra at room temperature of Mn 5+-doped Li 3PO 4 crystals are reported. A broad and strong ( σ ESA ≈ 1 × 10 −18 cm 2) ESA band due to the 1 E → 1 T 1 and 1 E → 1 T 2 transitions is observed between 10000 and 15000 cm −1 which prevents efficient near-infrared pumping for laser operation. For Mn 5+-doped Li 3PO 4 there is no ESA at the stimulated-emission wavelength, in contrast to the laser material Sr 5(VO 4) 3F:Mn 5+. This is due to the higher crystal field strength Δ and the weaker distortion of the host tetrahedron in Li 3PO 4. Finally, the laser potential of Mn 5+-doped materials, in general, is evaluated.

Stimulated emission spectra of powders of double sodium and lanthanum tetramolybdate

A study was made of the stimulated emission spectra of polycrystalline samples of Na5NdxLa1–x (MoO4)4 with diiferent neodymium concentrations. The stimulated emission wavelength of a mixture of powders with different concentrations of neodymium and slightly different spectra depended on the pump wavelength, indicating a mutual influence of the powder grains in the process of generation of stimulated radiation.

Study of a photochemical laser utilizing the XeO molecule

An experimental investigation was made of the performance of an XeO photochemical laser (stimulated emission wavelength 0.54 μ) operated at 160 °K. The observed dependence of the stimulated emission energy on the partial pressure of the N2–Xe–Ar active medium components is discussed. A combination of components is found which gives a specific energy output of ~8 mJ/cm3 and a total output energy of 0.6 J.

Stimulated emission from alexandrite (BeAl2O4:Cr3+)

A new laser material — alexandrite (BeAl2O4:Cr3+) — was investigated. Alexandrite crystals were grown from a molten mixture of BeO and Al2O3 taken in the stoichiometric ratio. The dimensions of the crystals reached 10×1×1 cm. The absorption spectrum at 300°K consisted of U and Y bands with maxima at 420 and 550–600 nm and of narrow lines B, R'1,2,3, and B1,2 at 465, 650–660, and 678.46–680.27 nm. Cooling to 77 °K shifted the R1,2 lines by 8 A toward shorter wavelengths. Stimulated emission of the R1 line was observed at liquid nitrogen temperature. The stimulated emission wavelength was within the range 679.86–680.33 nm.

Frequency conversion of neodymium laser radiation by resonant pumping of YAG crystals activated with Tm3+and Ho3+ions

Stimulated emission from Tm3+ and Ho3+ ions in an yttrium aluminum garnet (YAG) crystal was obtained for the first time by pumping with neodymium laser radiation via the absorption band of Yb3+. The stimulated emission wavelength of the Tm3+ ions was 2.014 μ and that of the Ho3+ ions was 2.09 μ. The room-temperature output energy was of the order of 10 mJ. The experimental results indicated that the efficiency of conversion of the neodymium laser wavelength to the 2 μ. range could be increased to values limited by the Stokes losses.

Laser threshold of viscous active media in the presence of induced absorption at stimulated emission wavelength

A calculation is made of the stimulated emission threshold of organic dye solutions as a function of the diffusion coefficient, intensity of induced singlet–singlet or triplet–triplet absorption at the stimulated emission wavelength, steepness of the leading edge of pump pulses, and other parameters. It is shown that, if the dipole moment of a fluorescence transition is perpendicular to the dipole moments of associated induced singlet–singlet or triplet–triplet absorption transitions, the laser threshold of high–viscosity solutions is considerably lower than that of low-viscosity systems. The maximum value of the ratio of the cross sections of the singlet-singlet absorption and stimulated emission, at which a given molecule ceases to emit stimulated radiation, increases from 1 to 3 when the rotational diffusion coefficient decreases from ∞ to 0.

Precision measurement of the stimulated emission wavelength and continuous tuning of YAIO3:Nd3+laser radiation due to4F3/2→4I13/2transition

Nonlinear optics methods were used in a precision measurement of the wavelengths of stimulated radiation (1339.3 and 1341.3 nm) emitted from Nd3+ ions in a YAIO3 crystal at 300°K as a result of the auxiliary transition 4F3/2→ 4I13/2. Continuous tuning of the frequency within the luminescence profiles of the investigated lines was achieved under various conditions. The results obtained were used also to refine the crystal-splitting scheme of the 4I13/2 multiplet of the Nd3+ ions in YAIO3.

Investigation of a multielement electron-beam-pumped semiconductor laser with an external mirror

An experimental investigation was made of a multielement semiconductor laser pumped longitudinally by an electron beam. When the inequality d < (2Lλ)1/2 (d is the distance between the laser elements, L is the distance to the external mirror, and λ is the stimulated emission wavelength) was satisfied, mode-locked operation was possible and this reduced the angular divergence of the ouput radiation. Amplified spontaneous radiation, reflected from an external mirror, had a considerable influence on the laser operation: It gave rise to a complex field pattern in the far zone and reduced the coherent output power until the laser action stopped altogether. The influence of the amplified spontaneous radiation increased with increasing total size of the multielement system.