Michael H. Anderson

Liquid crystal waveguides: new devices enabled by >1000 waves of optical phase control

A new electro-optic waveguide platform, which provides unprecedented voltage control over optical phase delays (> 2mm), with very low loss (< 0.5 dB/cm) and rapid response time (sub millisecond), will be presented. This technology, developed by Vescent Photonics, is based upon a unique liquid-crystal waveguide geometry, which exploits the tremendous electro-optic response of liquid crystals while circumventing their historic limitations. The waveguide geometry provides nematic relaxation speeds in the 10s of microseconds and LC scattering losses that are reduced by orders of magnitude from bulk transmissive LC optics. The exceedingly large optical phase delays accessible with this technology enable the design and construction of a new class of previously unrealizable photonic devices. Examples include: 2-D analog non-mechanical beamsteerers, chip-scale widely tunable lasers, chip-scale Fourier transform spectrometer (< 5 nm resolution demonstrated), widely tunable micro-ring resonators, tunable lenses, ultra-low power (< 5 microWatts) optical switches, true optical time delay devices for phased array antennas, and many more. All of these devices may benefit from established manufacturing technologies and ultimately may be as inexpensive as a calculator display. Furthermore, this new integrated photonic architecture has applications in a wide array of commercial and defense markets including: remote sensing, micro-LADAR, OCT, FSO, laser illumination, phased array radar, etc. Performance attributes of several example devices and application data will be presented. In particular, we will present a non-mechanical beamsteerer that steers light in both the horizontal and vertical dimensions.

A New Electro-Optic Waveguide Architecture and The Unprecedented Devices It Enables

A new electro-optic waveguide platform, which provides unprecedented electro-optical phase delays (> 1mm), with very low loss (< 0.5 dB/cm) and rapid response time (sub millisecond), is presented. This technology, developed by Vescent Photonics, is based upon a unique liquid-crystal waveguide geometry, which exploits the tremendous electro-optic response of liquid crystals while circumventing historic limitations of liquid crystals. The exceedingly large optical phase delays accessible with this technology enable the design and construction of a new class of previously unrealizable photonic devices. Examples include: a 1-D non-mechanical, analog beamsteerer with an 80° field of regard, a chip-scale widely tunable laser, a chip-scale Fourier transform spectrometer (< 5 nm resolution demonstrated), widely tunable micro-ring resonators, tunable lenses, ultra-low power (< 5 microWatts) optical switches, true optical time delay (up to 10 ns), and many more. All of these devices may benefit from established manufacturing technologies and ultimately may be as inexpensive as a calculator display. Furthermore, this new integrated photonic architecture has applications in a wide array of commercial and defense markets including: remote sensing, micro-LADAR, OCT, laser illumination, phased array radar, optical communications, etc. Performance attributes of several example devices are presented.

Polarimetry using liquid crystal variable retarders

A new technology for performing high-precision Stokes polarimetry is presented. One traditional Stokes polarimetry configuration relies on mechanical devices such as rapidly rotating waveplates that are undesirable in vibration-sensitive optics experiments. Another traditional technique requires division of a light signal into four components that are measured individually; this technique is limited to applications in which signal levels are sufficient that intensity reduction does not diminish the signal-to-noise ratio. A new technology presented here is similar to the rotating waveplate approach, but two liquid crystal variable retarders (LCVR’s) are used instead of waveplates. A Stokes polarimeter instrument based on this technology has been made commercially-available. The theory of operation is detailed, and an accuracy assessment was conducted. Measurement reproducibility was verified and used to produce empirical estimates of uncertainty in measured components of a Stokes vector. Uncertainty propagation was applied to polarization parameters calculated from Stokes vector components to further the accuracy assessment. A calibrated polarimeter measures four Stokes components with 10-3 precision and average predicted uncertainties less than ±2x10-3. An experiment was conducted in which the linear polarization angles were measured with a LC polarimeter and with a photodiode for comparison. Observed discrepancies between polarization angle measurements made with a polarimeter and those made with a photodetector were nominally within ±0.3°.

Next-generation photonic true time delay devices as enabled by a new electro-optic architecture

We present new photonic-true-time-delay (PTTD) devices, which are a key component for phased array antenna (PAA) and phased array radar (PAR) systems. These new devices, which are highly manufacturable, provide the previously unattainable combination of large time delay tunability and low insertion loss, in a form factor that enables integration of many channels in a compact package with very modest power consumption. The low size, weight, and power are especially advantageous for satellite deployment. These devices are enabled by: i) “Optical Path Reflectors” or OPRs that compresses a >20 foot change in optical path length, i.e., a >20 nsec tuning of delay, into a very compact package (only centimeters), and ii) electro-optic angle actuators that can be used to voltage tune or voltage select the optical time delay. We have designed and built OPRs that demonstrated: large time delay tunability (<30 nsecs), high RF bandwidth (>40 GHz and likely much higher), high resolution (<200 psec), and low and constant insertion loss (< 1 dB and varying by < 0.5 dB). We also completed a full design and manufacturing run of improved EO angle actuators that met the PTTD scanner requirements. Finally, a complete optical model of these integrated devices will be presented, specifically; the design for a multi-channel (400 channels) PTTD device will be discussed. The applicability and/or risks for space deployment will be discussed.

New electro-optic laser scanners for small-sat to ground laser communication links

In this paper we present new electro-optic beam steering technology and propose to combine it with optical telecommunication technology, thereby enabling low cost, compact, and rugged free space optical (FSO) communication modules for small-sat applications. Small satellite applications, particularly those characterized as “micro-sats” are often highly constrained by their ability to provide high bandwidth science data to the ground. This will often limit the relevance of even highly capable payloads due to the lack of data availability. FSO modules with unprecedented cost and size, weight, and power (SWaP) advantages will enable multi-access FSO networks to spread across previously inaccessible platforms. An example system would fit within a few cubic inch volume, require less than 1 watt of power and be able to provide ground station tracking (including orbital motion over wide angles and jitter correction) with a 50 to 100 Mbps downlink and no moving parts. This is possible, for the first time, because of emergent and unprecedented electro-optic (EO) laser scanners which will replace expensive, heavy, and power-consuming gimbal mechanisms. In this paper we will describe the design, construction, and performance of these new scanners. Specific examples to be discussed include an all electro-optic beamsteer with a 60 degree by 40 degree field of view. We will also present designs for a cube-sat to ground flight demonstration. This development would provide a significant enhancement in capabilities for future NASA and other Government and industry space projects.

Chip scale broadly tunable laser for laser spectrometer

We are developing an innovative Tunable Laser Spectrometer (TLS) that is compact, broad tuning range (> 200 nm) enabled by an innovative chip-scale (a waveguide based architecture), non-mechanical (voltage- controlled tuning), Waveguide External-cavity Semiconductor Laser (WECSL). This WECSL based TLS, with broad tuning range, will enable the simultaneous measurement of multiple gases abundances in Martian and other planetary atmospheres, adsorbed to soil; and bound to rocks. This monolithic, robust, integrated-optic Tunable Laser Absorption Spectrometer (TLS) will operate in the near infrared and infrared spectral bands. The system architecture, principles of operation and applications of the TLS will be reported in this paper.

Liquid crystal clad waveguide laser scanner and waveguide amplifier for LADAR and sensing applications

We will describe the construction and performance of a prototype high speed, non-mechanically scanned, laser system that is coupled to a custom planar waveguide optical amplifier. The system provides high speed (10 kHz) scanning of <200 far-field resolvable spots, with a path toward <500 spots at 10 kHz demonstrated. An enabling component for this system is the new EO scanner that provides previously unrealizable performance such as sub-millisecond scanning, full 2-D operation with only three control electrodes, fully refractive (no side-lobes) scanning, no blind spot within the field of view (FOV), and a large continuous scan angle. Scanners with near perfect Gaussian output beams, throughputs greater than 50%, and a 500 × 15o continuous field-of-view will be discussed. Furthermore, a path toward much larger FOVs will also be presented. We will also present the design and construction of custom planar waveguide amplifiers to which our EO scanner can be free space end-fire coupled. The amplifiers and scanners were designed for operation at 1.645 microns. This will enable long-range, eye-safe LADAR and sensing applications, such as CH4 sensors.

Miniature, compact laser system for ultracold atom sensors

As ultracold atom sensors begin to see their way to the field, there is a growing need for small, accurate, and robust laser systems to cool and manipulate atoms for sensing applications such as magnetometers, gravimeters, atomic clocks and inertial sensing. In this paper we present a frequency-agile, butterfly packaged laser source, absolutely referenced to an atomic transition. We also present the entire laser system, including a fiber-coupled optical amplifier and liquid crystal shutters, replacing a laboratory table’s worth of optics with a system the size of a paperback novel.

A new photonics technology platform and its applicability for coded aperture techniques

An emergent electro-optic technology platform, liquid crystal (LC) waveguides, will be presented with a focus on performance attributes that may be relevant to coded aperture approaches. As a low cost and low SWaP alternative to more traditional approaches (e.g. galvos, MEMs, traditional EO techniques, etc.), LC-Waveguides provide a new technique for switching, phase shifting, steering, focusing, and generally controlling light. LC-waveguides provide tremendous continuous voltage control over optical phase delays (> 2mm demonstrated), with very low loss (< 0.5 dB/cm) and rapid response time. The electro-evanescent architecture exploits the tremendous electro-optic response of liquid crystals (can be > one million pm/Volts) while circumventing their historic limitations; speeds can be in the microseconds and LC scattering losses can be reduced by orders of magnitude from conventional LC optics. This enables a new class of photonic devices: very wide analog non-mechanical beamsteerers (270° demonstrated), chip-scale widely tunable lasers (50 nm demonstrated), chip-scale Fourier transform spectrometers (< 5 nm resolution demonstrated), widely tunable micro-ring resonators, tunable lenses (fl tuning from 5 mm to infinity demonstrated), ultra-low power (< 5 microWatts) optical switches, true optical time delay devices (12 nsecs demonstrated) for phased array antennas, and many more. Both the limitations and the opportunity provided by this technology for use in coded aperture schemes will be discussed.