Products:
Integrated Optical Devices
Integrated Holographic Devices
Integrated holographic technology offers a broad and powerful platform for chip-level optical devices requiring high performance spectral filtering, spectral signature recognition, multiplexing, temporal waveform shaping or processing, and complex on-chip signal routing or wavefront control. Integrated holographic devices may be either fully 2D (holographic Bragg reflector) or 1D (channel waveguide) based. They may be fabricated in high performance silica-on-silicon formats, in active semiconductor materials, or in polymeric materials using nano-imprinting or stamping. Integrated holographic products may be implemented in single- and multi-mode formats addressing high performance telecommunications applications as well as cost sensitive data/LAN applications. Integrated holographic fabrication methods employ standard wafer-based tools developed for the semiconductor industry. Each fabricated wafer yields several hundred fully functional optical chips. Unlike thin film filters and other bulk optics-based components, an integrated holographic chip is monolithic and does not require multiple assembly steps. Integrated holographic product solutions can provide unprecedented combinations of cost and performance across a wide range of applications. In the paragraphs below, we highlight certain product areas currently under development.
Holographic Bragg Reflector Multiplexers
Holographic Bragg Reflector (HBR) based multiplexers have multiple superior attributes relative to performance and cost including:
- Very small die size - HBR devices achieve spectral resolution determined by the actual device size. This aspect of HBR behavior is dramatically different from arrayed waveguide grating (AWG) based multiplexers where spectral resolution derives from path differences substantially smaller than the actual device.
- Excellent passband profile control - in HBR devices, the internal arrangement of diffractive contours provides complete control over the spectral passband of each multiplexer channel. There is no insertion loss penalty for flat-top versus Gaussian or other designer passband profiles. Passband control applies to both CWDM and DWDM environments.
- Mixed channel spacing/passband - since each multiplexer channel is controlled by an independent HBR, channel separations and passbands may be independently specified.
- Fully integrated solutions for CWDM and DWDM applications - HBR multiplexer technology is fully consistent with the broad bandwidths and widely spaced channels of CWDM as well as the more closely spaced and narrower DWDM configurations.
- Single-sided die - the retro-reflective nature of HBR devices provides for single-sided die device configuration. A single fiber-attach process lowers costs and enhances yield.
- Immunity to point fabrication defects - optical signals within an HBR-based device are spatially delocalized. As such, some point fabrication errors that would render AWG-type devices inoperative will not lead to significant performance degradation and therefore enhance fabrication yield.
- Compatibility with multifunction photonic circuits - HBR-based multiplexers are fully compatible, especially by virtue of their small footprint, with multi-function integrated photonic solutions. The HBR fabrication process is compatible with most standard photonic integration formats.
Holographic Bragg Reflector Spectral Filters/Sensors
Spectral filtering is important for a multitude of commercial, military, and scientific applications ranging from spectral target recognition to remote sensing. Holographic Bragg reflectors (HBRs) have powerful spectral filtering capability. HBR spectral filters offer improvements over both fiber-Bragg-grating filters and thin-film filters.
- HBR filters are fully integrated with physically distinct input and output ports.
- Input signal from a single port may be coupled to an array of output ports with a separate transfer function for each thereby providing real-time spectral signature analysis.
- Spectral transfer functions supported may be simple (flat-top window) or extremely complex (matching a molecular spectrum with hundreds of lines).
- Resolution of approximately 10 GHz in 1-cm size devices with reflective bandwidth/resolution ratios of thousands.
Optical Processors
Spectral filtering and optical processing are closely related functions. The temporal waveform of an input signal can be cross-correlated against a reference waveform by passing it through a spectral filter whose complex-valued transfer function is appropriately related to the reference waveform. HBR filtering devices may be designed to provide fully coherent amplitude and phase controlled spectral transfer functions and may thus provide cross-correlation function. HBR devices linking a single input signal to multiple output ports with each linking providing a different spectral transfer function (and hence reference correlation) allow comparison of input optical data to a whole array of reference temporal signatures. Instead of providing correlation function, spectral filters can be configured to provide temporal waveform coding of input data bits. HBR-based optical processing devices, single- or multi-channel, provide powerful support for advanced optical communication systems (optical code-division multiplexing, optical header decoding, etc.) and other applications requiring optical waveform analysis or control.
Channel Waveguide Grating Filters
DUV photolithographic fabrication allows for the integration of powerful grating-based filtering function into the channel waveguides employed by traditional photonic integrated circuits (PICs). Patented LightSmyth approaches to channel waveguide grating apodization provide a unique pathway to new PIC functionality. Unlike traditional UV-written fiber Bragg gratings, channel waveguide gratings produced via photolithography allow for highly reproducible and accurate apodization with superior throughput.
Photonic Transport Fabric
Integrated holographic structures, with their distributed, signal-specific interaction, offer a profoundly different approach to the processing and routing of optical signals in integrated photonic environments. Rather than utilizing signal confinement as in electronic analog channel-waveguide and photonic crystal circuit architectures, integrated holographic structures allow for delocalized, overlapping signals and control structures. One can envision a future photonic circuit configured with integrated holographic structures that focus, collimate, spectrally filter, or cross-correlate signals as they route them to their intended receiver - all without regard for other optical data streams simultaneously present whether spatially coincident or not. The flexibility of design offers entirely new integrated photonic circuit architectures and is highly relevant to optical interconnect applications such as inter- and intra-chip communications. As to why integrated holographics and advanced photonic transport capability is suddenly possible, one must note advances in computer design and most importantly sub-micron pixel-by-pixel fabrication capability. The time and opportunity for profoundly photonic, delocalized, integrated circuits is finally in hand. Look for exciting developments.
Custom Integrated Holographic Devices
Integrated holographic devices can be configured to provide flexible spectral filtering, temporal/spectral waveform programming, multiplexing, and many other functions (see our articles section for more details). They can be implemented as slab or channel waveguide grating devices or as tailored surface diffractive optical structures for reflective or transmissive free-space beam shaping, spectral dispersion, or focusing. They can be engineered at the 100-200 nm scale with spatial coherence over centimeters.
LightSmyth Technologies technical expertise can assist companies, universities, or government agencies in creating custom-designed integrated holographic devices for special applications, R&D, or evaluation. For university-level R&D, there is a special funding source for obtaining technically innovative products. Interested university customers should consult the Photonics Technology Access Program (PTAP) for details.
Custom devices can be processed either as stand-alone or shared-access projects, with the latter providing lower costs but longer delivery time because of the need to group multiple customers to share masking and processing costs.
Our experienced design and fabrication team can assist you in harnessing this powerful new technology for use in your products. Please contact us at info@lightysmyth.com with any questions, input or application needs.