Characterization and evaluation of acid-modified starch of Dioscorea oppositifolia (Chinese yam) as a binder in chloroquine phosphate tablets

Chinese yam (Dioscorea oppositifolia) starch modified by acid hydrolysis was characterized and compared with native starch as a binder in chloroquine phosphate tablet formulations. The physicochemical and compressional properties (using density measurements and the Heckel and Kawakita equations) of modified Chinese yam starch were determined, and its quantitative effects as a binder on the mechanical and release properties of chloroquine phosphate were analyzed using a 2³ full factorial design. The nature (X1), concentration of starch (X2) and packing fraction (X3) were taken as independent variables and the crushing strength-friability ratio (CSFR), disintegration time (DT) and dissolution time (t80) as dependent variables. Acid-modified Chinese yam starch showed a marked reduction (p<0.05) in amylose content and viscosity but increased swelling and water-binding properties. The modified starch had a faster onset and greater amount of plastic flow. Changing the binder from native to acid-modified form led to significant increases (p<0.05) in CSFR and DT but a decrease in t80. An increase in binder concentration and packing fraction gave similar results for CSFR and DT only. These results suggest that acid-modified Chinese yam starches may be useful as tablet binders when high bond strength and fast dissolution are required

High power CW red VECSEL with linearly polarized TEM00 output beam

High-power, continuous-wave operation at red wavelengths has been achieved with a vertical external cavity surface emitting laser based on the GaInP/AlGaInP/GaAs material system. Output power of 0.4W was obtained in a linearly polarized, circularly symmetric, diffraction-limited beam. A birefringent filter inserted in the cavity allowed tuning of the laser output spectrum over a 10nm range around 674nm

Red microchip VECSEL array

We report an InGaP/AlInGaP/GaAs microchip vertical-external-cavity surface emitting laser operating directly at red wavelengths and demonstrate its potential for array-format operation. Optical pumping with up to 3.3W at 532nm produced a maximum output power of 330mW at 675nm, in a single circularly-symmetric beam with M2<2. Simultaneous pumping with three separate input beams, generated using a diffractive optical element, achieved lasing from three discrete areas of the same chip. Output power of ~95mW per beam was obtained from this 3×1 array, each beam having a Gaussian intensity profile with M2<1.2. In a further development, a spatial light modulator allowed computer control over the orientation and separation of the pump beams, and hence dynamic control over the configuration of the VECSEL array

Tunable red laser emission by intra-cavity doubling of a GaInNAs VECSEL

Oral presentation on wavelength-tunable CW red laser emission by intra-cavity frequency-doubling of a 1320nm GaInNAs semiconductor thindisk laser. Initial results show tuning over 16.4nm with up to 4.9mW of output power

Microchip vertical-external cavity surface-emitting laser using a concave-shaped diamond micromirror

This paper demonstrates a plano-concave microchip vertical-external cavity emitting laser (mu-VECSEL) operating at 1.05 mum. The cavity is composed of a semiconductor structure, comprising an active region grown on top of a distributed Bragg reflector (DBR), and a diamond heatspreader with its outer surface shaped as a spherical microlens. This stable optical cavity has a signal spot diameter of ~19.8 mum on the active region and of ~21 mum at the concave micro-mirror facet

Diamond-microchip GaInNAs vertical external-cavity surface-emitting laser operating CW at 1315nm

What is believed to be the first microchip-format vertical external-cavity surface-emitting laser (VECSEL) operating at 1.3 μm is reported. Fundamental-mode continuous-wave output powers >120 mW were achieved from a cavity volume ∼0.001 mm3 using a diode-pumped GaInNAs VECSEL structure capillary-bonded to a dielectric-mirror-coated single-crystal diamond heatspreader