Abstract: The present application relates to a semiconductor laser, in particular such a laser which operates with substantially single longitudinal mode emission. The laser comprising a laser cavity, the laser further comprising a slot having an interface, characterized in that the slot is substantially filled with a reflective material having a large imaginary index relative to the laser cavity material. The interfaces of the slot may be inclined or may have a step for introducing a quarter wave phase shift.

Abstract: The present application provides a semiconductor Fabry-Perot dual mode lasing device having terahertz characteristics resulting in significant advantages over the prior art including for example operation at room temperatures and the absence of re-growth processing requirements.

Abstract: Disclosed is a laser (10) comprising a lasing cavity with a lasing medium and primary optical feedback means in the form of a facet (17) at either end of the cavity, the laser cavity defining a longitudinally extending optical path; and secondary optical feedback means formed by a plurality of refractive index perturbations (16, 22) in the laser cavity, each perturbation defining two interfaces (20, 21); characterized in that, for at least one perturbation, only one of the two interfaces contributes to optical feedback along the optical path. The present invention relaxes the lithographic tolerances for making single longitudinal mode devices and improves performance characteristics.

Abstract: The present application is directed at providing a new lasing device having increased production yields over other single mode laser devices. In particular, a semiconductor lasing device is provided having at least two lasing devices formed on a common substrate. The lasing device is arranged so that in use a preferred lasing device is operational and remaining lasing devices are redundant. This redundancy improves the production yield since only one of the lasing devices needs to function correctly as the others are unused.

Abstract: The present application relates to a semiconductor laser, in particular such a laser which operates with substantially single longitudinal mode emission. The laser comprising a laser cavity, the laser further comprising a slot having an interface, characterised in that the slot is substantially filled with a reflective material having a large imaginary index relative to the laser cavity material. The interfaces of the slot may be inclined or may have a step for introducing a quarter wave phase shift.

Abstract: The present invention relates in general to semiconductor light emitting devices and in particular to methods of altering the spatial emission patterns of such devices. A known problem with these prior art light emitting devices (and laser diodes in general) is that their far-field emission patterns are elliptical and astigmatic in nature. The present invention addresses this problem by refractive index perurbations in the semiconductor device aligned in a direction substantially transverse to the light emission direction to achieve a desired spatial distribution of the emission.

Abstract: Disclosed is a laser (10) comprising a lasing cavity with a lasing medium and primary optical feedback means in the form of a facet (17) at either end of the cavity, the laser cavity defining a longitudinally extending optical path; and secondary optical feedback means formed by a plurality of refractive index perturbations (16, 22) in the laser cavity, each perturbation defining two interfaces (20, 21); characterised in that, for at least one perturbation, only one of the two interfaces contributes to optical feedback along the optical path. The present invention relaxes the lithographic tolerances for making single longitudinal mode devices and improves performance characteristics.

Abstract: A laser comprising a lasing cavity, having a lasing medium and primary optical feedback means in the form of a facet at either end of the cavity is described. The laser includes secondary optical feedback means in the form of one or more effective refractive index perturbations in the lasing cavity with at least one of the facets configured to preferentially reflects a specific wavelength or band of wavelengths. A method of manufacturing such a laser is also described as is a method of suppressing side modes in a lasing device.

Abstract: A method of distinguishing, from a moving platform, stationary objects from moving objects. The method includes using a first detector mounted to the moving platform to obtain at least a first reading from a target area, advancing the moving platform relative to the target area and using a second detector mounted to said moving platform to obtain at least a second reading from said target area. Then, the method includes comparing said first and second readings for at least two different time intervals to distinguish moving objects from stationary objects.

Abstract: A device for detecting humans includes a radio frequency transmitter for generating a signal in a frequency range in which human bodies absorb RF radiation. A radio frequency receiver is spaced relative to the radio frequency transmitter for receiving a portion of the signal. A human passageway is provided between the transmitter and receiver. The receiver includes a detector responsive to a change in the received portion of the signal for determining the passing by of a human. The detector is responsive to an amplitude and/or phase change in the received portion of the signal. A building access security system or people counting system would include a plurality of devices set up in adjacent lanes. The RF detection system may be augmented with the addition of an IR detection beam system, distance sensors and/or a video camera system. The video camera system may include stereo video.

Abstract: An obstacle detection method and system for a barrier closure system comprising a sensor for measuring a predetermined parameter as it varies during a closure of a barrier. Memory stores the measured parameter to establish a first parameter profile and a threshold value associated therewith. A detection module compares a current value of the predetermined parameter to a corresponding barrier position of the first parameter profile and if the current value differs by more than a threshold value sets an obstacle detection state. Conveniently the profile is recalibrated to compensate for changes in the barrier closure system such as wear, and environmental conditions that may vary over time. Preferably the sensor includes a capacitance component.