Continuous-wave Blue Laser Research Articles

Observation of infrared interband luminescence in magnesium by femtosecond spectroscopy

Ultrafast luminescence in Mg was investigated in the infrared region, between 0.35 and 1.05 eV, and compared with the results for Al, using a luminescence upconversion technique. The luminescence intensity of these metals at 0.9 eV was higher than that of platinum with a similar surface roughness under the same excitation density. Although the Mg and Al are adjacent to each other in the periodic table and belong to “light metals,” having similar band structures, their luminescence spectra differ significantly. Pronounced peak structures were found for Mg and these were attributed to interband transitions within the conduction bands consisting of 3s and 3p orbitals overlapped on the intraband continuum, based on density functional theory band structure calculation. This result is in contrast to the interband luminescence in noble metals (Au, Ag, and Cu) under continuous-wave blue laser excitation, where the final states have been assigned to the d bands. A comparison of the spectra of rough and specular surfaces suggested that the surface roughness is not essential for mitigating wavenumber mismatch for intraband transitions. The luminescence from light metals, which are harmless to humans, will be attractive for biomedical applications.

Intracavity cascade pumped 493.1nm blue laser

In this paper, a continuous-wave(CW) blue laser based on intracavity cascade pumping sum-frequency technology is designed. This system generates quasi-three-level laser through LD end-pumped Nd:YAG crystal, and then intracavity pumps Yb:YAG crystal to achieve 946 nm and 1030 nm laser in the cavity. Finally, a type-I critical phase-matched LBO is used for intracavity sum-frequency to achieve CW blue laser output at 493.1 nm. In the experiment, a compact linear resonator was adopted, and a 493.1 nm blue laser of 426 mW was obtained for a pump power of 25 W. Its optical to optical conversion efficiency is 1.7 %. The beam quality factors M2 in the x and y directions are 1.28 and 1.31, respectively. The power instability of the blue laser output is less than 3.2 % within 2 h.

Low-Temperature Fabrication of High Quality Gate Insulator in Metal–Oxide–Semiconductor Capacitor Using Laser Annealing

This letter reports the fabrication of a high quality gate oxide for metal–oxide–semiconductor field-effect transistors using a continuous-wave blue laser. A thin Zr metal layer was inserted between the dielectric and substrate to increase laser absorption and reduce the interface layer. A simulation of laser irradiation showed that the metal layer insertion induces a significant increase in temperature during laser annealing compared with the dielectric without a metal layer. The laser annealed capacitor with a 1-nm-thick Zr metal layer showed superior electrical characteristics, such as high capacitance, low leakage current, low fixed charge density, and low interface state density. Based on these results and the economic advantage of blue laser diodes, this technique can be a solution for low temperature processes, such as monolithic 3-dimensional integration, where low temperature processes are required.

Deposition of Fine Linewidth Silver Layer using a Modified Laser-induced Forward Transfer Technique

This paper reports the deposition of a metal line using a multilayer stack and laser-induced forward transfer (LIFT) using a low cost continuous wave blue laser with a wavelength of 450 nm. The donor structure was composed of a light-to-heat (LTH) layer, a release layer, and a transfer layer in series. Amorphous silicon as the LTH layer absorbs photon energy and converts it to heat. A release layer was melted so that a silver transfer layer would be transferred to the receiver substrate. The transferred silver layer showed reasonable physical and electrical characteristics. A low cost fine linewidth metal layer could be achieved using this modified LIFT technique and blue laser.

Pure-three-level Yb:GdCOB CW laser at 976 nm.

We present what is, to the best of our knowledge, the first pure-three-level Yb:Ca4GdO(BO3)3 (Yb:GdCOB) laser emitting at 976nm based on the F5/22-F27/2 transition, generally used for a quasi-three-level emission at 1032nm. A maximum power of 782mW at 976nm has been achieved in continuous-wave (CW) operation pumped by a quasi-three-level Nd:SrLaAlO4 laser emitting at 902nm. Moreover, a self-frequency-doubling CW blue laser has also been demonstrated with a maximum power of 133mW at 488nm.

57‐2: Scalable Crystallization of a‐Si Film on a Glass Substrate by Using a Blue Laser

A continuous-wave blue laser annealing (BLA) system (λ ~ 440 nm) is applied to delineate the physical phenomenon of low-temperature crystallization from amorphous Si (a-Si) thin film to poly-Si film on glass substrates for potential industrial application. At various scanning speeds and laser intensities, crystallization mechanism of BLA has been studied. It shows that BLA can achieve high quality, smooth poly-Si film with laterally grown grains with sizes of 4×10 µm, as studied by optical microscopy, Raman spectroscopy, and AFM. The p-channel poly-Si TFT on glass exhibited the field-effect mobility of 120.82 cm2/Vs and subthreshold swing of 284mV/dec. Therefore, it proves that BLA can substitute conventional annealing processes as a reliable, scalable, and economical tool.

Low temperature polycrystalline silicon with single orientation on glass by blue laser annealing

We report the achievement of low-temperature polycrystalline silicon (LTPS) thin-films with a single orientation on glass by using continuous wave blue laser annealing (BLA) of amorphous silicon (a-Si). The BLA is administered in multiple shots and with increasing number of shots, grain size increases and all grains follow a single orientation. Because the absorption coefficient of a blue laser (BL) in poly-Si is less than that in a-Si, the amount of the un-melted Si at the bottom is gradually reduced with increasing number of shots, resulting in near complete melting of the whole Si layer. In this study, irradiation of a 150-nm-thick a-Si film with 200 BL (445nm) shots achieves a poly-Si film having an average grain size of about 4μm and single orientation in the (100) direction.

P-7: High Performance LTPS Thin-film Transistors using Low Cost Polycrystalline Silicon by Blue Laser Annealing

Crystallization of amorphous silicon (a-Si) to polycrystalline silicon (p-Si) by a continuous-wave blue laser diode of wavelength 445 nm is investigated for high throughput thin-film transistor applications (TFT). As the laser scan speed is changed at constant laser power, laser scanned p-Si films show three kinds of grain shape that can be distinguished according to grain growth mechanism: (1) solid phase crystallization (SPC), (2) partial melting growth (PMG), and (3) full melting growth (FMG). These three growth mechanisms are as a result of different laser irradiation time to a-Si and relative absorbed laser energy difference, therefore, they achieve different grain size and crystallinity. By using this blue laser annealing (BLA) system, we can obtain the high performance and low cost low temperature polycrystalline silicon (LTPS) TFTs with large grain size.

Completely solid-state LD-side-pumped Nd:YAlO3 CW blue laser with intracavity frequency tripling

We report a completely solid-state continuous-wave (CW) blue laser operating at 447 nm utilizing intracavity frequency tripling of an LD-side-pumped Nd:YAlO3 (Nd:YAP) laser operating at 1341.4 nm. An LBO crystal with type-I critical phase matching and a KTP crystal with type-II critical phase matching (CTM) were used for the second harmonic generation (SHG) and the third harmonic generation (THG), respectively. In view of the analysis of the cavity stability, a four-mirror folded cavity was designed and the output characteristics were theoretically analyzed. Experimental characteristics obtained were shown to be in agreement with the theoretical analysis. The maximum output power of the 447 nm CW blue laser reached 114 mW, which corresponds to a red-to-blue conversion efficiency of 9%.

Hyperspectral laser-induced fluorescence imaging for assessing apple fruit quality

Chlorophyll fluorescence is a promising technique for postharvest quality research, and reported studies were mainly based on the fluorescence kinetic analysis method, which has not been quite satisfactory for measuring fruit quality. This paper reports on using a hyperspectral imaging technique for measurement of laser-induced fluorescence from apple fruit for predicting multiple fruit quality parameters. A continuous wave blue laser (408 nm) was used as an excitation source for inducing fluorescence in apples. Fluorescence scattering images were acquired from ‘Golden Delicious’ apples by a hyperspectral imaging system at the instance of laser illumination (0 min) and after 1, 2, 3, 4, and 5 min of illumination. The hyperspectral fluorescence image data were represented by mean, maximum, and standard deviation spectra. Standard tests were performed on measuring fruit skin and flesh color, firmness, soluble solids content, and titratable acid. A hybrid method of combining principal component analysis and neural network modeling was used for developing prediction models to predict fruit quality parameters for each of the six illumination time periods. Fluorescence emission decreased steadily during the first 3 min of illumination and was stable within 5 min. The 0-min fluorescence prediction models had somewhat poorer prediction results for individual quality parameters except skin hue than did the models of longer illumination time. The differences were minimal in the model prediction results from the fluorescence data at 1, 2, 3, 4 or 5 min of illumination. Overall, excellent predictions were obtained for apple skin hue with the correlation coefficient of prediction of 0.94. Relatively good predictions were obtained for fruit firmness, skin chroma, and flesh hue with values for the correlation coefficient being equal to or greater than 0.74 for 1 min of illumination or longer times, and poorer correlations were found for soluble solids content, titratable acid, and flesh chroma. Hyperspectral laser-induced fluorescence imaging is potentially useful for assessing selected quality parameters of apple fruit and further research is needed to improve fluorescence measurement for better prediction of fruit quality.

Compact continuous-wave blue lasers by direct frequency doubling of laser diodes with periodically poled lithium niobate waveguide crystals

A compact continuous-wave blue laser has been demonstrated by direct frequency doubling of a laser diode with a periodically poled lithium niobate (PPLN) waveguide crystal. The optimum PPLN temperature is near 28 degrees C, and the dependence of waveguide crystals on crystal temperature is less sensitive than that of bulk crystals. A total of 14.8 mW of 488-nm laser power has been achieved.

Tunable blue light generation by sum-frequencymixing of AlGaAs and InGaAs laser diodes in KNbO 3

A 25 mW continuous-wave blue laser is demonstrated by noncritical type I phase-matched sum-frequency mixing of a master-oscillator power-amplifier InGaAs laser diode and an AlGaAs laser diode in a potassium niobate (KNbO3) crystal. The blue laser is continuously tunable over the wavelength range from 431 to 438 nm.