A wavelength division multiplexer that integrates an axial gradient refractive index element with a diffraction grating to provide coupling from a plurality of input optical sources (each delivering a single wavelength) which are multiplexed to a single polychromatic beam for output to a single output optical receiver. The device comprises means for accepting optical input from at least one optical source, the means including a planar surface (20a); a coupler element (20) comprising an axial gradient refractive index collimating lens (26) having a planar entrance surface onto which the optical input is incident and a homogeneous index boot lens (24, 28) affixed to the axial gradient refractive index collimating lens and having a planar but tilted exit surface (20b); a diffraction grating (22) on the tilted surface of the homogeneous index boot lens which combines a plurality of spatially separated wavelengths from the optical light; and means to output at least one multiplexed, polychromatic output beam, the means including a planar surface (20a). The device may be operated in the forward or reverse direction as a multiplexer or demultiplexer.

Integrated bi-directional axial gradient refractive index/diffraction grating wavelength division multiplexer

A holographic optical device includes a light-transmissive substrate, a first holographic optical element, and a second holographic optical element that is laterally disposed on the substrate from the first holographic optical element At least one of the holographic optical elements is a complex diffraction grating that can handle a multiplicity of plane and/or spherical waves arriving from a range of angles, and having a range of wavelengths Applications for the device include a wavelength division multiplexer/demultiplexer, an image reconstructor, a beam expander/compressor, and a visor/head-up display

Holographic optical devices for the transmission of optical signals of a plurality of channels

A holographic optical device having a light transmissive substrate with a first holographic optical element carried by the substrate, and a second holographic optical element also carried by the substrate but laterally offset from the first holographic optical element. The first holographic optical element diffracts waves from each data point in a display source into a collimated plane wave such that the plane wave is trapped inside the substrate by internal reflection, and the first holographic optical element also corrects field aberrations over the entire field of view by being recorded using at least one aspheric wavefront. The second holographic optical element diffracts the trapped plane waves out of the substrate.

Planar holographic optical device

Apparatus and methods for altering one or more spectral, spatial, or temporal characteristics of a light-emitting device are disclosed. Generally, such apparatus may include a volume Bragg grating (VBG) element that receives input light generated by a light-emitting device, conditions one or more characteristics of the input light, and causes the light-emitting device to generate light having the one or more characteristics of the conditioned light.

Use of volume bragg gratings for the conditioning of laser emission characteristics

Scalable Network Architectures Using the Optical Transpose Interconnection System (OTIS)

The optical transpose interconnection system uses a simple pair of lenslet arrays to implement a one-to-one interconnection that is useful for shuffle-based multistage interconnection networks, mesh-of-trees matrix processors, and hypercubes.

Optical transpose interconnection system architectures.

We present theoretical and experimental results of a novel fiber-optic wavelength-division multiplexing (WDM) design employing a broadband (>150-nm) dichromated gelatin volume holographic grating operating in a reflective Littrow configuration with on-axis optics, a single lens, and one fiber array. This configuration can achieve better than −1.5-dB insertion loss and −40-dB cross talk for a 6-channel system and −2.5-dB insertion loss and −20-dB cross talk for a 12-channel system with 15-nm channel spacing. For an experimental 4-channel WDM unit we measured better than −1.5-dB insertion loss for all channels and less than −32-dB cross talk. This design can provide cost and performance benefits for local area network communication applications.

Fiber-optic wavelength-division multiplexing and demultiplexing using volume holographic gratings.

A photorefractive beam splitter (PRBS) is introduced as an alternative to a polarizing beam splitter (PBS) for coupling optical power into reflective modulators in a free-space optical interconnection system. The PRBS uses a single diffraction grating recorded in a photorefractive material to redirect the incident laser light into the first diffraction order and onto the modulators. Reflected interconnection light not matching the Bragg angle criteria transmits uncoupled through the beam splitter. Experimental results show that the PRBS provides better, more uniform transmission for off-axis beams than the currently used PBS.

Photorefractive beam splitter for free-space optical interconnections

A method is presented for compensating cavity thickness variations in conventional Fabry–Perot devices through the replacement of the input mirror with a holographic mirror, resulting in a self-tuned Fabry–Perot (STFP) device. The technique is suitable for integrating large arrays of electro-optic Fabry–Perot modulators with silicon circuitry. Experimental results of a STFP modulator are presented showing cavity thickness compensation of an electrooptic 9/65/35 bulk lead lanthanum zirconate titanate crystal having thickness variations corresponding to ∼6 Fabry–Perot fringes in a 2.5×2.5 mm2 area. The compensated modulator used an in situ recorded Fe-doped LiNbO3 holographic mirror, and had a uniform backreflection over a 2.5×2.5 mm2 area.

Thickness variation compensation in a fabry-perot modulator array using a self-tuned fabry-perot structure

The design, analysis and experimental demonstration of the motionless-head parallel readout optical disk system are presented. The system is designed to read 1-D data blocks distributed radially on the disk’s active surface and generate 2-D output binary images [*I. It has the unique advantage that no mechanical motion of the head is required for fast access, focusing or Wdcking. This allows a data rate of up to 1 Gbytdsec for standard disk rotation speeds of 2400 rpm. The data blocks are stored on the disk as 1-D Fourier-transform Computer Generated Holograms (CGH). Each one of them is calculated to reconstruct one column of a 2-D output image. During the sequential recording process, all the CGH for a given 2-D image are laid-out side by side and radially shifted from one another until they span the entire radius of the disk active surface. During the parallel readout process, only the data blocks a single image are illuminated at once and data access is achieved solely through the disk rotation so that the entire memory can be read in one rotation. The Fourier direction of the holograms is along the radial direction of the disk. Thus, due to the shift invariance properties of Fourier transform holograms, the tracking servo requirement can be eliminated. Under-illuminated Fourier Transform holograms will still reconstruct, although with a loss in output signal-to-noise ratio. Therefore, the information redundancy property of Fourier Transform holograms virtually eliminates the focus servo requirement. An iterative CGH encoding method is developed to produce high signal-to-noise ratio reconstructions and to reduce significantly the radial alignment requirements of the recorded data bits. The iterative algorithm is derived fiom the DBS technique and in conjunction with a gray level representation by area modulation on the disk, it is proven to give the best results if compared to existing conventional encoding schemes. The optical readout system simply consists of three stationary cylindrical lenses. The fmt one illuminates an area on the disk that corresponds to the data blocks of a single output 2-D image. For better optical performance and signal uniformity, it can be replaced by a single diffractive beam forming element (Fresnel hologram). The other two

Phil Harvey

Papers

Optical transpose interconnection system architectures.

Fiber-optic wavelength-division multiplexing and demultiplexing using volume holographic gratings.

Photorefractive beam splitter for free-space optical interconnections

Thickness variation compensation in a fabry-perot modulator array using a self-tuned fabry-perot structure

Motionless-head Parallel Readout Optical Disk Prototype System