Abstract: Provided is a laser module. The laser module comprises: a substrate; an gain unit oscillating a laser light on the substrate; an external resonance reflecting unit total-reflecting the laser light at an external of the substrate adjacent to one side of the gain unit; and an inner resonance reflecting unit reflecting the laser light to the external resonance reflecting unit at the substrate between the modulating unit and gain unit and outputting the laser light to the modulating unit.

Abstract: Provided is a frequency-tunable terahertz light source device. The frequency-tunable terahertz light source device satisfies a Littrow diffraction condition at a wavelength and simultaneously satisfies a Littman-Metcalf diffraction condition at another wavelength using a double diffraction grating having two grating periods. Thus, oscillations simultaneously occur at the two different wavelengths, such that a terahertz wave can be stably generated by beating of the two oscillation wavelengths. In addition, the frequency-tunable terahertz light source device can readily change a frequency up to several terahertz and can be fabricated in a small size.

Abstract: A wavelength tunable laser diode using a double coupled ring resonator is provided. A new double coupled ring resonator structure is formed by a connection of two ring resonators having different radii so that stable laser oscillation occurs only in a resonant wavelength at which the two ring resonators are simultaneously resonated, and the effective refractive index of the two ring resonators is properly controlled differently for tunable laser oscillation wavelengths. The reproducibility of the optical coupling characteristics of the passive waveguides and the ring resonator can be assured by multi-mode couplers. This results in improved manufacturing productivity of the wavelength tunable laser diode. It is possible to amplify and output an output light without having an effect on oscillation wavelength characteristic by means of an optical amplifier integrated in an output end.

Abstract: Provided is a frequency-tunable terahertz light source device. The frequency-tunable terahertz light source device satisfies a Littrow diffraction condition at a wavelength and simultaneously satisfies a Littman-Metcalf diffraction condition at another wavelength using a double diffraction grating having two grating periods. Thus, oscillations simultaneously occur at the two different wavelengths, such that a terahertz wave can be stably generated by beating of the two oscillation wavelengths. In addition, the frequency-tunable terahertz light source device can readily change a frequency up to several terahertz and can be fabricated in a small size.

Abstract: The present invention relates to a Bacillus sp. strain producing a mannanase which is highly active in the neutral and the acidic media. The Bacillus sp. WL-1 strain (KCTC 0800BP), which is isolated from the soil, produces in large scale the mannanase in the culture medium containing lactose and bran, wherein the mannanase is highly active in the neutral and the acidic media so said mannanase is useful as an additive for feeds and is helpful in the decomposition of hemicellulose.

Abstract: The present invention relates to a Bacillus sp. strain producing a mannanase which is highly active in the neutral and the acidic media. The Bacillus sp. WL-1 strain (KCTC 0800BP), which is isolated from the soil, produces in large scale the mannanase in the culture medium containing lactose and bran, wherein the mannanase is highly active in the neutral and the acidic media so said mannanase is useful as an additive for feeds and is helpful in the decomposition of hemicellulose.