This PDF file contains the front matter associated with SPIE Proceedings Volume 11125 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Multilayer optical data storage is a promising approach for realizing archival optical discs with terabyte capacity for applications in enterprise data storage. We report on the fabrication of optical discs containing 16 layers from a high-scalable multilayer polymer film co-extrusion process. Polymer co-extrusion is a well-established roll-to-roll manufacturing process with applications as diverse as food packaging and high performance optical filters. We have adapted this to produce films with alternating active and buffer layers. The film is easily fabricated into optical discs with the potential capacity of several terabytes. Data is stored in voxels defined by photobleaching a fluorescent or reflective dye contained in writable layers of 200-300nm thickness separated by inert layers of 2-3 microns. We have shown that at short pulse durations of a pulse-modulated commercial 405nm laser, the nonlinear writing process within the absorption band of the dye exhibits a distinct threshold, thus promising low crosstalk and sub-diffraction limit bit patterns. Results on writing physics will be presented. We have recently demonstrated that data can be written and read using a novel optical pick-up. The confocal optical configuration for reading suggests that the drive developed for our discs could be backward compatible with earlier commercial optical discs. Studies of photostability and defect density suggest the suitability of this technology for long-term, high-performance enterprise archival data storage.

The huge volume of digital information generated across the world represents an insuperable challenge for the currently-available data storage devices and compels for the development of novel techniques and storage media. Nanomaterials, which have unique mechanical, electronic and optical properties owing to the strong confinement of electrons, photons and phonons at the nanoscale, are enabling the development of disruptive methods for optical data storage with ultra-high capacity, ultra-long lifetime and ultra-low energy consumption. In this context, upconversion nanoparticles, which feature the interesting property of photon upconversion and emit in a range from ultraviolet to near-infrared, have attracted considerable attention for optical data storage applications through the modulation of their upconversion fluorescence emission. However, it has been difficult to find an effective quencher for upconversion nanoparticles to entirely quench their anti-Stokes type of emission. Graphene oxide (GO) and reduced graphene oxide (r-GO) have proved useful as effective quenchers due to their strong broadband absorption. Herein, we demonstrate optical data storage in a GO and upconversion nanoparticles thin film. Core-shell nanoparticles were prepared via co-precipitation method and measurements of upconversion fluorescence emission intensity and fluorescence lifetime have been performed. Subsequently, the upconversion nanoparticles have been conjugated to GO and deposited through vacuum filtration to form a thin film. The nanocomposite was then irradiated using laser at different powers to produce the reduction of GO to r-GO. The encoded optical data bits were readout through the variation of fluorescence intensity from the upconversion nanoparticles accompanied by the reduction of the GO to r-GO.

The efficiency of a communication channel is basically determined by its signal to noise ratio. Digital data is reliable but its rigorous waveform has extra information. So, it should occasionally be converted to an analog modulated signal suitable for the channel. I have demonstrated an application and improvement of the Orthogonal Frequency Division Multiplexing (OFDM) method to optical disc systems. The frequency sub-band separation scheme not only has the advantage of the efficient use of the channel, but also seems to be valid for perturbations in practical use of optical disc systems. I will discuss about the tolerance of the OFDM readout to the perturbations such as defocus, disc tilt and so on. Some variations of sub-band separation and improvements such as the suppression of peak to average power ratio is another issue. In order to implement the OFDM for an optical disc system, it is necessary to perform analog signal recording. One of the method available is the Delta-Sigma conversion method. Using this method, an analog signal is converted to a binary digital waveform that can be used to modulate the light pulses for recording. However, the recording characteristics of media is not linear in general. An arrangement of the method in addition to the simulation with a typical optical recording model will be discussed.

Heat-assisted magnetic recording (HAMR) is a promising technology for achieving more than 10 Tbit/inch² recording density. A near-field transducer (NFT), which forms a small light spot on a recording medium, is necessary in HAMR. However, the heat generated by the NFT would melt the NFT itself. To solve this problem, the authors have proposed a novel device, in which a metal nano-antenna is attached to a semiconductor ring resonator. In this paper, the near-field light generated by the semiconductor ring resonator with the metal nano-antenna was analyzed through a numerical simulation to optimize the structure of the device. The simulation was conducted using the finite element method based on a 3-dimensional model. It was found that how to excite a desired eigenmode selectively among some eigenmodes is important to make the device effective, and that various design parameters such as the length of the nano-antenna and the distance between the ring resonator and the nano-antenna can be optimized.

The original image has been processed by sampling, calculating and encoding to achieve a-Si based hologram patterns using MATLAB. Through the investigation of the relationship between laser fluences and phase modulations (π), the calculated hologram pattern has been fabricated with femtosecond laser processing. The holographic image is captured using CCD by illuminating the hologram patterns with 561 nm laser beam. The conversion efficiency of 0.82% has been measured using an optical meter.

Adaptive Optics (AO) is an established technique for improving image quality and compensating for aberrations induced by focusing through samples with varying thickness and refractive index. Future optical data storage schemes with multiple data layers may require the correction capabilities of AO systems. However, the diffractive phase introduced by light reflected from optical storage media might be problematic for high-performance systems. A laser beam focused onto grooved media has a reflection with a baseball-shaped variation in the pupil, caused by the overlap in diffracted orders with the zero-order reflection. This pupil variation is significant in intensity, and simulations and experiments show that there is an associated small variation in phase. If the diffractive phase is sufficiently small, measurement of the total phase with aberrations by a wavefront sensor could enable application of AO correction with diffractive media samples. Simulations and experiments are presented to examine the capability of an adaptive optics microscope system to compensate for diffractive effects with a coherently illuminated sample. AO systems are commonly implemented with incoherent objects, but this could be extended to other applications by characterizing the performance of an AO system with a coherent reflection from a diffractive surface. Data storage media are used as targets for investigating these intensity and phase variations caused by coherence effects, with well-defined grating parameters creating diffraction patterns that are modeled and verified experimentally. There are potential applications outside of data storage, such as coherent freespace optical communication.

This paper presents a patent pending approach to store digital data using high bandwidth laser light in motion. Data is stored in a loop. The amount of data stored is the data rate times the storage time. Lyteloop uses: (i) highly multiplexed optical communications to maximize data rate, and (ii) a long light path, to maximize length of time it takes light to traverse the full storage loop. Lyteloop is developing data storage in motion in 4 domains : fiber, space, and two forms of near vacuum chambers. Multiplexing is done across very wide wavelength ranges, and many spatial modes. OEM modes will be used in free space at the shorter wavelengths, and other spatial mode structures will be used in fibers. Multiple cores will be used in fibers. A 1.5 Gigabyte demonstation data storage unit has been built in fiber, and is described, along with its performance. We are starting a free space prototype. Lyteloop builds on, and advances, both free space, and fiber, high data rate communications technology as a method of storing data in motion. We also have patent pending approaches to increase the length of the data stroage loop. Less complex, and lower power, signal regeneration will be required to achive Lytelops’s goals.

In-vehicle head-up displays (HUDs) are now being marketed. Such a HUD is intended as an augmented reality (AR) display that provide a safe driving environment by showing information derived from vehicle sensor data. A laser HUD is optimal for an AR display because it can effectively call the information it displays to the driver’s attention and displays a seamless image with a wide color gamut and high brightness contrast. We have developed a projection unit for an automotive laser HUD and have achieved high image quality and reliability, which were previously issues with laser projection units, by developing a new screen and two-axis micro-electromechanical systems (MEMS) mirror.

Most of information from the outside world is obtained through our eyes. Various colors make the world distinguishable and our life rich and colorful. To achieve the best imaging and displaying of our colorful world is the ultimate dream of human-being in all ages, which is also the main issue of Optics. Among different obstacles, the chromatic aberration directly brought from the intrinsic material property and phase accumulation at different wavelengths may be the most severe problem in a full-color optical system. Here, by using the IRU (integrated resonance unit elements) based metasurface, the first perfect achromatic lens at the visible region has been demonstrated, with only wavelength scale thickness that is quite desirable in the integrated Optics and daily life, such as in the cell-phone camera. Compared with the traditional (bulky) achromatic lenses or objectives, our achromatic metalens presents perfect achromatism in a continuous bandwidth rather than the traditional solution only suppressing the chromatic aberration at discrete wavelengths. In metalens field, our result is also far ahead in competition with other reported works. In comparison to the ordinary metalens, our broadband achromatic metalens demonstrates high transmission efficiency (about 60% at peak) in visible spectrum without chromatic aberration. The achieved continuous achromatism in visible region enables us to obtaining the first metalens-based full-color imaging. Recently, we demonstrate the full-color light-field imaging based on the broadband achromatic metalens array, which is considered as a signifcant progress for metalens imaging.

Lensless light-field imaging with Fresnel zone aperture (FZA) is a technology that enables lensless cameras with beneficial features such as light calculation load in the image reconstruction processing, and refocusing, i.e. post-capturing focus adjustment. The ability to refocus indicates that the lensless camera s 3D information of the scene and the depth information can be extracted through comparison of contrasts among reconstructed images at different focus distances. This feature is promising since monocular 3D sensing can be achieved without using special light sources. However, since exhaustive search is needed to extract depth information, application of the contrast method is unsuitable for purposes that require real-time depth sensing. To overcome this limitation, we aimed to establish a new fast 3D sensing algorithm for lensless cameras with FZA. The proposed algorithm is based on our findings that reconstructed images of the lensless camera are complex images that have values in real and imaginary parts, and the sign of the imaginary part is reversed when the focus position of the lensless camera crosses the in-focus position. Since this "zero-crossing point" can be calculated through simple interpolations, 3D sensing can be achieved without exhaustively searching over numbers of reconstructed images with various focus positions. We have verified the effectiveness of the algorithm through simulation and experiments with developed prototypes. The algorithm enables real-time compact 3D sensors suitable for various applications, e.g. smartphones, robots, and vehicles.

An auto lidar design will start with a corner case such as a small child stepping out from between parked cars at a range. The size, and range, of the object to be detected determine required angular resolution. The range depends on the speed of the auto, which determines stopping distance. An auto lidar should be designed to have a range longer than the required stopping distance by some distance margin. A lidar designer concerned about urban driving will not require as long a range as a designer concerned about the autobahn. Some auto lidars will scan in elevation, but others will use an array of detectors to cover the full elevation, and just scan in azimuth. A long range lidar is more likely to only cover a frontal azimuth region, such as 120 degrees, whereas a shorter range lidar is likely to cover 360 degrees in elevation. It is more likely longer range lidars will be at eye safer wavelengths, such as 1550 nm. To keep cost down many designers prefer diode lasers instead of fibers, but diode lasers cannot be Q switched, so have low peak power. Most auto lidars today are pulsed, so if the designer uses diode lasers there will usually be one laser per detector, whereas with a fiber laser there may only be a single laser illuminating a line that is viewed by a detector array.

Lidar, radar, optical imaging and ultrasonic are important environmental sensing technologies in the field of autonomous driving. Among them, the radar can perform long-distance sensing, however it is limited by the resolution and cannot distinguish objects. Optical images have clear object resolving power, but hardly to get distance information. Ultrasonic only detect objects that are in very short distances. Therefore, it is necessary to have a technique that can clearly distinguish the objects and get the object information such as speed and distance at medium-range (100-m) for autonomous driving scheme entering level 4 and level 5. The existing light technology in the autonomous driving is to place the Lidar module on the roof of a car and perform environment sensing in a rotating manner. Such technology has low sensing capability and is not conform to the development direction of the vehicle industry that not fulfill the demand of autonomous car. In contrast to Lidar module on the roof, placing the Lidar on the front of the car has many advantages, such as easy to collect dust, suffer water corrosion and difficult to set up the electrical system. Integrating the Lidar with headlight system is a feasible direction to solve the aforementioned problems. In this study, we will develop laser headlights system with Lidar module by integrating the optical system of Lidar into headlight a unit, in which the smart laser headlight was achieved by feedback control orders system. The laser headlight will focus on the development of smart headlights with laser as the light source. With the feedback of the system, it can control the car's light field, avoid high-reflection areas at night. The integrated Lidar module will develop a quasi-static optical scanning system with a wavelength of 1550 nm and embed it in the optical path of the laser headlight. By wavelength differences, the optical path of Lidar does not interfere with headlight and high quality optical data could be obtained. Despite adapting 905 nm as optical wavelength in the current technology, the 1550 nm wavelength selected by this study meets the safety regulations and will not cause damage to the human eye at night or during the day. In this study, we will develop a Lidar module attached to a 10W laser headlight for autonomous driving. The simulation and optical performance of integration of Lidar module with laser headlight will be presented.

Laser beam steering technology is essential for modern consumer and scientific optical devices including displays, microscopy, and Light Detection and Ranging (LIDAR) systems. Along with mechanical and completely non-mechanical beam steering approaches, Micro Electro Mechanical Systems (MEMS) are emerging beam steering devices that are especially suitable for LIDAR systems due to their fast scan rate and large scan angle. A class of MEMS-based devices, the Digital Micromirror Device (DMD), has been demonstrated for beam steering too by synchronizing its mirror movement to laser pulse. The tilt movement of micromirrors synchronizes with multiple pulses from multiple laser sources that sequentially redirect the pulses to multiple diffraction orders within μs. Based on the beam steering principle, multi-beam and multi-pulse beam steering in single-chip DMD LIDAR architecture provides a pathway to fast distance range finding having over 1M samples/s scan rate by leveraging a commercially available DMD, laser diodes and drivers. As a proof of concept, 3.34kHz and 15 points of range finding is demonstrated by using three pulsed laser diodes operating at 905nm. Additionally, multi-pulse beam steering for 5 points with an increased scanning rate of 6.63kHz demonstrates further enhancement of the scanning speed. The approach opens up a pathway to achieve a LIDAR system with a scanning rate over 1M samples/s while leveraging a state of the art DMD and a moderate number of laser sources.

A range compensating lens design in the return channel for active optical systems, e.g., range finders and LiDARs, is detailed and several examples analyzed using raytrace methods. This proposed range compensating lens, which reduces the “one over range squared” attenuation, is described by Mudge [Appl. Opt., (2019)]. The motivation of the lens is to reduce the return signal with targets (objects) relatively near and boost the signal at far range targets by combining lens elements in parallel rather than in series, as typically done. Using the technique provided in the reference, to include field angle details, a designer can develop a lens requiring a detector with less dynamic range and/or extend the far range limit while maintaining the minimum target distance. We provide discussion to implement this approach along with a variety of examples of this range compensating lens to cover design techniques needed for the return lens desired and include some penalties incurred.

In this paper, an electrostatically actuated MEMS micromirror with enhanced stroke is presented. Unlike traditional MEMS micromirror, the proposed micromirror achieves a large out-of-plane stroke through employing a larger air gap for the micromirror surface to move as well as eliminating the pull-in instability. This novel micromirror has a central reflective micromirror surface of 400 μm by 400 μm, an L-shaped arm that holds the micromirror to the anchor on all side and 3 fixed bottom electrodes beneath each L-shaped arms. The lateral electrostatic forces on the upper L-shaped arm are equal in magnitude but opposite in direction and they counteract to neutralize out each other. The electrostatic force produced on the top L-shaped arm is larger than on the bottom. Therefore, the net electrostatic force points in the upward direction. As a result, the upper plate of the micromirror moves upwards. COMSOL Multiphysics is used to simulate and design the device in order to optimize the stroke of the micromirror for a lower input voltage. The mirror is fabricated using PolyMUMPs fabrication technique where an air cavity of 2.75 μm was achieved by combining the two available sacrificial layers. In this proposed design, an out-of-plane stroke of 2.43 μm is achieved at a 110 V DC bias voltage.