Aurora’s automotive frequency-modulated continuous-wave (FMCW) lidar technology has been designed and developed to address the needs of level 4/5 autonomous vehicles (AVs). Aurora’s FirstLight provides eye-safe and long-range performance, radial velocity on every point, and high spatial density. These features allow the Aurora Driver to unlock faster perception, tracking, and classification of vehicles and pedestrians.
Fiber-based optical technology developed for coherent telecom applications including EDFA’s had been employed for most coherent lidar applications. High power diode lasers and semiconductor optical amplifiers offer an exciting route to reduce the complexity and improve robustness over fiber-based FMCW laser technology. A highly integrated semiconductor FMCW lidar system would greatly aid size, weight, and power considerations while removing dependence on optical fibers which are typically a point of higher manufacturing costs and performance susceptibility
Ultra-high sensitivity sensors can be achieved with optically levitated particles in ultra-high vacuum (UHV). Trapped particles act as high-Q harmonic oscillators, whose amplitude, position, and frequency can be monitored to provide high sensitivity measurements of the particle’s acceleration. Larger particles (10-30 microns in diameter) provide higher sensitivity, but they are difficult to trap in UHV without particle loss. To overcome the radiometric forces that lead to particle loss, rare earth (RE) ion dopants can be incorporated into the particles to enable solid-state laser cooling of the particle’s internal temperature. The laser used for optical trapping can be tuned to a wavelength on the lower energy side of the ion absorption band, and thus also serve as the pump laser for solid-state laser cooling. Internal cooling occurs when the average energy of the photons emitted is larger than the average energy of the photons absorbed. Ions will rapidly thermalize while in the ground and the excited states to create the energy difference. Solid-state laser cooling has been realized in bulk host materials and is well understood. This technique of internal cooling for reducing loss pressure is currently being tested.
We developed a confocal microscope and ultra-spectral light source containing Liquid Crystal Arrayed Microcavities (LCAM) as a new technology for controlled ultra-narrow optical filtering (FWHM ∼0.1 nm). LCAMs use picoliter volume Fabry–Perot-type optical cavities filled with liquid crystal for wavelength tuning. With sub-nanometer spectral resolution, we measured spectral resonance from scattering particles to validate the measurements with simulation results. We measured chicken liver and breast muscle, pig skin and muscle and compared with results from literature. The main application is the estimation of nuclear size in biological tissues for noninvasive assessment equivalent to histopathology.
Currently large volume, high accuracy three-dimensional (3D) metrology is dominated by laser trackers, which typically utilize a laser scanner and cooperative reflector to estimate points on a given surface. The dependency upon the placement of cooperative targets dramatically inhibits the speed at which metrology can be conducted. To increase speed, laser scanners or structured illumination systems can be used directly on the surface of interest. Both approaches are restricted in their axial and lateral resolution at longer stand-off distances due to the diffraction limit of the optics used. Holographic aperture ladar (HAL) and synthetic aperture ladar (SAL) can enhance the lateral resolution of an imaging system by synthesizing much larger apertures by digitally combining measurements from multiple smaller apertures. Both of these approaches only produce two-dimensional imagery and are therefore not suitable for large volume 3D metrology. We combined the SAL and HAL approaches to create a swept frequency digital holographic 3D imaging system that provides rapid measurement speed for surface coverage with unprecedented axial and lateral resolution at longer standoff ranges. The technique yields a “data cube” of Fourier domain data, which can be processed with a 3D Fourier transform to reveal a 3D estimate of the surface. In this paper, we provide the theoretical background for the technique and show experimental results based on an ultra-wideband frequency modulated continuous wave (FMCW) chirped heterodyne ranging system showing ~100 micron lateral and axial precisions at >2 m standoff distances.
Compressive laser ranging (CLR) is a method that exploits the sparsity available in the range domain using compressive
sensing methods to directly obtain range domain information. Conventional ranging methods are marred by requirements
of high bandwidth analog detection which includes severe SNR fall off with bandwidth in analog-to-digital conversion
(ADC). Compressive laser ranging solves this problem by obtaining sub-centimeter resolution while using low
bandwidth detection. High rate digital pulse pattern generators and off the shelf photonic devices are used to modulate
the transmitted and received light from a superluminescent diode. CLR detection is demonstrated using low bandwidth,
high dynamic range detectors along with photon counting techniques. The use of an incoherent source eliminates speckle
issues and enables simplified CLR methods to get multi-target range profiles with 1-3cm resolution. Using compressive
sensing methods CLR allows direct range measurements in the sub-Nyquist regime while reducing system resources, in
particular the need for high bandwidth ADC.
We describe progress toward an optical lattice clock based on an even isotope of Yb. The 1S0 → 3P0 clock
resonance in 174Yb is accessed through a magnetically induced spectroscopic technique. Using ≈1mT static
magnetic fields and ≈10 μW of probe light power we generate Rabi frequencies of several hertz. The narrow
spectroscopic features that result (< 10 Hz FWHM) require a highly stabilized laser at the clock transition
wavelength of 578 nm. We describe a new all solid-state laser system that shows hertz level stability. In order
to cancel the slow drift of the cavity, spectroscopy is performed on the clock transition to provide feedback to
the laser. Using a Ca neutral atom frequency standard as a reference oscillator,we show high stability and an
effective method for investigating clock frequency shift systematics.
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