Abstract: A grating has a high diffraction efficiency into the minus first diffracted order in transmission, for both TE and TM polarizations. The incident angle may optionally be chosen so that the minus first diffracted order in reflection would be retroreflected back to the incident beam. The grating may be formed from various materials and/or layers, where the thicknesses of the individual layers may be determined by an optimization or simulation process. In one aspect, the grating may have four or more layers, formed with three or more materials. In another aspect, the grating may have a longitudinal refractive index profile that contains at least two local extrema, such as a maximum and/or minimum. Such a grating may be formed from three or more materials, two materials, or a single material that has a continuously varying refractive index. Any or all of the materials may have a continuously varying refractive index profile, as well.

Abstract: Transmission spectrometers require low levels of background light so that the signal to noise ratio is increased, and also require stable performance over wide temperature ranges. Light reflected by the transmission grating can result in increased background levels. One approach to reducing the background level is to orient the transmissive diffraction grating so that light reflected by the grating is reflected out of the diffraction plane. The temperature-induced wavelength drift of a transmission spectrometer can be due to the frame upon which the transmission grating is mounted. The wavelength drift is reduced by allowing the thermal expansion of the grating to be independent of the frame.

Abstract: A wavelength division multiplexed device is based on a transmission grating spectrometer having at least two diffractive optical elements. The WDM device provides flexible use and may be widely applied in WDM systems. The device is useful for multiplexing and demultiplexing, channel monitoring, for adding and dropping channels, and for controlling the power in individual channels within a multiple channel signal. The device provides for dynamic control of individual channels, and may be advantageous in use as a gain flattening filter.

Abstract: A wavelength division multiplexed device is based on a transmission grating spectrometer having at least two diffractive optical elements. The WDM device provides flexible use and may be widely applied in WDM systems. The device is useful for multiplexing and demultiplexing, channel monitoring, and for adding and dropping channels. The device provides programmability in use as an add/drop multiplexer.

Abstract: In a method of making a replication tool, replication parts for both two dimensional optical elements, such as are fabricated using micro-forming techniques, and three dimensional optical elements, that are typically formed using cutting techniques are present on the replication tool. A method of manufacturing a replication tool for a planar optical sheet includes mounting at least one optical element part on a base to form a master part and forming a conductive metal layer over the master part. The method also comprises electrochemically depositing over the conductive metal layer to form an electrochemically deposited layer, separating the electrochemically deposited layer from the master part. The invention also relates to the replication tool itself and optical circuits formed using the replication tool.

Abstract: A method and apparatus for measuring spectral information of light from at least one object includes at least one light detector and at least one transparent body. The transparent body has a front side that has an entrance aperture and at least one reflecting surface. The transparent body also has a back side that includes at least one reflecting surface and an exit surface. The detector is positioned near the exit surface. At least one of the front reflecting surface and the back reflecting surface includes a diffractive optical element arranged to receive diverging light from the aperture. A focusing element focuses diffracted light to the exit surface. The apparatus may comprise multiple channels and may also include a device for measuring a distance to the object.

Abstract: Transmission spectrometers require low levels of background light so that the signal to noise ratio is increased, and also require stable performance over wide temperature ranges. Light reflected by the transmission grating can result in increased background levels. One approach to reducing the background level is to orient the transmissive diffraction grating so that light reflected by the grating is reflected out of the diffraction plane. The temperature-induced wavelength drift of a transmission spectrometer can be due to the frame upon which the transmission grating is mounted. The wavelength drift is reduced by allowing the thermal expansion of the grating to be independent of the frame.

Abstract: A method and apparatus are presented for aligning a diffractive WDM device that includes i) a multi-channel, light handling device having a selected channel spacing and ii) a multi-channel signal input unit. The method includes adjusting a direction of incidence of an optical signal from the input unit on at least a first diffracting element of the WDM device so as to set an actual optical channel spacing at an output region of the WDM device to be approximately equal to the selected channel spacing of the multi-channel, light handling device. In the apparatus, the orientation of the light input unit is adjustable in a direction parallel to a diffraction plane of the diffractive WDM device so as to select an actual channel spacing at the multi-channel, light handling device that is approximately equal to the selected channel spacing.

Abstract: New grating structures include a bonded transmission grating structure. The grating structure is encapsulated by two pieces that are bonded together. In addition, a new method of making grating structures includes forming wells with an aspect ratio (depth:width) of at least 3:1, 7:1 or greater. Such grating structures can be used to form gratings with high diffraction efficiencies for both TE and TM polarizations of light.

Abstract: An improved technique of exposing a photoresist through a grating mask reduces the occurrence of overlapping gratings and also avoids distortions in the exposed mask when there is a gap between the contact mask and the photoresist layer. The technique is particularly well suited to forming Bragg gratings on semiconductors and other materials that are used for wavelength selection in, for example, optical communications applications. The technique employs a phase grating held close to, but out of contact with, the photoresist layer. Amongst the advantages provided by the present invention is that the requirements of the permissible thickness of the photoresist layer suitable for writing high visibility gratings are relaxed, thus reducing the complexity and costs for processing the substrate.