Abstract: Optical components are flip chip mounted onto a substrate for improved alignment. Each device is fabricated using “build-up” layers above a substrate. Each has an optical confinement region in which optical radiation travels in use, and a bonding surface. The overall depth of the layers above the optical confinement region is closely controlled during fabrication, for instance by the use a “spacer” layer, so that when the devices are subsequently flip chip mounted adjacent one another on a shared substrate by means of their bonding surfaces, they can be passively positioned so that their optical confinement regions abut and optical radiation can be coupled from one to the next in use.

Abstract: An optical characterization device has a guiding body and a diffractive structure integrated with it. The guiding body delivers radiation to the diffractive structure at a preselected angle and the diffractive structure diffracts at least a portion of radiation guided to it to give spatial resolution according to wavelength. A position sensitive detector detects the position of the spatially resolved radiation and thus the radiation can be characterized according to wavelength. Embodiments can be used to monitor and adjust the wavelength of a radiation source, using a feedback connection. By using the integrated approach, a very small structure can be realized and the structure can be relatively simply fabricated and assembled. The guiding body might be either capable of supporting multimode propagation of the radiation or might be a single mode waveguide. Where it is capable of supporting multimode propagation, an input to the guiding body acts to select a mode for propagation of the radiation.

Abstract: In a tunable optical source, a diffraction device 115 is used to provide wavelength selective feedback to a laser diode 100. The diffraction device 115 is at least partially fabricated in a material whose refractive index is controllable so as to control the diffraction performance of the device. This allows the diffraction device 115 to be used in tuning the optical source, potentially without using moving parts. For instance, the refractive index can be controlled using a temperature change across material of the device 115. The diffraction device 115 can be mounted in free space in an external cavity with respect to the laser diode 100. Novel forms of diffraction device 115 are described. Tunable optical sources of this type can be used for instance in communications, particularly wavelength division multiplexing.

Abstract: In a tunable optical source, a zone plate device 100 is used to provide frequency selective feedback to a laser diode 110. The zone plate device 100 is positioned to receive an output mode of the laser diode 110 and to return a frequency selected image of the mode spot to the laser diode 110. By changing the refractive index of material of the zone plate device 100, it is possible to change the frequency providing the image at the point of return to the laser diode 110. This allows the zone plate device 100 to be used in tuning the optical source, without using moving parts. In an embodiment, the zone plate device 100 is at least partially fabricated in an electro-optic material such as SBN:75 and can therefore be tuned by using electrodes to apply an elecric field across it. The zone plate device 100 can be coupled directly to the laser diode 110 or via a waveguide section 105 which can be used to increase the output mode spot size from the laser diode 110 for delivery to the zone plate device 100.

Abstract: A tunable optical source comprises a laser diode and an external optical feedback device. The feedback device has a waveguiding portion fabricated at least in part out of a glass material having both organic and inorganic components. A control device is provided for controlling the refractive index of the glass material so as to change the wavelength of feedback to the laser diode. The glass material may for example have thermo-optic properties and the control device might then be a heating device for heating the glass material. The feedback device can have more than one portion, a second portion for example having controllable coupling characteristics for coupling optical radiation into or out of the feedback device. It also preferably has a portion for controlling optical path length in the feedback device.

Abstract: Optical components are flip chip mounted onto a substrate for improved alignment. Each device is fabricated using “build-up” layers above a substrate. Each has an optical confinement region in which optical radiation travels in use, and a bonding surface. The overall depth of the layers above the optical confinement region is closely controlled during fabrication, for instance by the use a “spacer” layer, so that when the devices are subsequently flip chip mounted adjacent one another on a shared substrate by means of their bonding surfaces, they can be passively positioned so that their optical confinement regions abut and optical radiation can be coupled from one to the next in use.