Digital Micromirror Device Research Articles

Low-cost printed holography for the generation ofstructured light.

Recently, the study of structured light fields has attracted great interest, which includes their generation and characterization techniques, as well as their application. Most of these techniques rely on the use of expensive devices, such as liquid crystal spatial light modulators or digital micromirror devices that also require specialized knowledge and software. In this work, we present a scheme for producing low-cost amplitude holograms for the generation of structured light fields. We demonstrate the feasibility of this technique by creating a variety of paraxial modes, such as the well-known Laguerre-Gaussian and Hermite-Gaussian beams. We also demonstrate the potential of our technique in solving the phase retrieval problem to generate 2D and 3D holographic images of objects. Finally, we compare our proposal with the typical generation techniques using digital micromirror devices. Our proposal will pave the path for the generation of structured light beams in more affordable ways for the application in undergrad laboratories.

Enhanced Asymmetric Light‐Plasmon Coupling in Graphene Nanoribbons for High‐Efficiency Transmissive Infrared Modulation

AbstractGraphene plasmonic modulators can manipulate the mid‐infrared light in transmission mode, which is currently challenging for traditional liquid crystal and digital micromirror devices, opening up a new avenue for infrared scene projection, infrared optical communication, and hyper spectra imaging. Nevertheless, their efficiencies are not high enough due to the single‐layer atomic thickness and low free carrier density of graphene. Here, it is demonstrated that the modulation efficiency can be significantly improved by enhancing the asymmetric light‐plasmon coupling. A general theoretical model is established to describe the modulation behaviors of the modulator, revealing the critical role of the asymmetric coupling rate. By using dielectric environment engineering and graphene structure design experimentally to enhance the asymmetric coupling rate from 0.45×1012 to 7.05×1012 s−1, the modulation efficiency has been improved from 4% to 41% at 1530 cm−1, while maintaining the bandwidth as large as 230 cm−1. The modulator outperforms previous transmission‐type graphene plasmonic modulators in both efficiency and bandwidth, presenting great potential in next‐generation infrared integrated photonics platforms.

Flexible generation of broadly wavelength- and OAM-tunable Laguerre-Gaussian (LG) modes from a random fiber laser.

Broadband wavelength tunable Laguerre-Gaussian (LG) mode with flexibly manipulated topological charge is greatly desired for large-capacity optical communication. However, the operating wavelengths achieved for the current LG modes are significantly restricted either by the emission spectrum of the intracavity gain medium or by the operation wavelengths of mode-conversion or modulation components. Here, broadband wavelength-tunable LG modes with a controllable topological charge are generated based on a random fiber laser (RFL) and a digital micromirror device (DMD). The RFL can produce broadly wavelength-tunable laser emissions spanning from 1044 to 1403 nm with a high spectral purity and an excellent beam quality, benefiting from the cascaded random Raman gain starting from a ytterbium fiber based active gain. A commercially available broadband DMD is then utilized to excite the LG modes with a flexibly tunable topological charge of up to 100 order through the super-pixel wavefront shaping technique. The combination of the RFL and the DMD greatly broadens the operating wavelength region of the LG modes to be achieved, which facilitates the capacity scaling-up in the orbital angular momentum multiplexed optical communication application.

Three-Dimensional Printing of Large Objects with High Resolution by Dynamic Projection Scanning Lithography.

Due to the development of printing materials, light-cured 3D printing is playing an increasingly important role in industrial and consumer markets for prototype manufacturing and conceptual design due to its advantages in high-precision and high-surface finish. Despite its widespread use, it is still difficult to achieve the 3D printing requirements of large volume, high resolution, and high speed. Currently, traditional light-cured 3D printing technologies based on stereolithography, such as regular DLP and SLA, can no longer meet the requirements of the processing size and processing rate. This paper introduces a dynamic projection of 3D printing technology utilizing a digital micro-mirror device (DMD). By projecting the ultraviolet light pattern in the form of "animation", the printing resin is continuously cured in the exposure process to form the required three-dimensional structure. To print large-size objects, the three-dimensional model is sliced into high-resolution sectional images, and each layer of the sectional image is further divided into sub-regional images. These images are dynamically exposed to the light-curing material and are synchronized with the scanning motion of the projection lens to form a static exposure pattern in the construction area. Combined with the digital super-resolution, this system can achieve the layering and fine printing of large-size objects up to 400 × 400 × 200 mm, with a minimum feature size of 45 μm. This technology can achieve large-size, high-precision structural printing in industrial fields such as automobiles and aviation, promoting structural design, performance verification, product pre-production, and final part processing. Its printing speed and material bending characteristics are superior to existing DLP light-curing 3D printing methods.

Design of an optical illumination system for a long wave infrared scene projector based on diffraction characteristics.

This study proposes an optical illumination system design based on vector diffraction characteristics and the Scheimpflug principle to determine an optimal relationship between illumination uniformity, energy utilization, and system size in an infrared scene projector. We investigate the influence of digital micromirror device (DMD) diffraction efficiency at different incidence angles on energy utilization rate and establish a two-dimensional diffraction grating model to determine the optimal incidence angle of the DMD beam. We demonstrate that the optical illumination system of a long-wave infrared (LWIR) scene projector based on diffraction characteristics can simulate an infrared scene with a compact structure, high energy efficiency, and high uniformity.

(Invited) The Importance of Characterizing and Calibrating Light Engines in Vat Photopolymerization Additive Manufacturing

Vat photopolymerization (VP) is an additive manufacturing technique that uses spatially patterned light to cure liquid resins into solid materials. As an additive manufacturing technique, parts with complex geometries can be manufactured that would not be possible with conventional techniques. Large scale VP has found wide adoption by a range of industries including automotive, dental, consumer goods, and prototyping. On a smaller scale, hobbyist level users have found innumerable uses for VP and this market, in particular, has fueled the development of a plethora of low-cost printers. Common to all VP printers is the need for a light engine which illuminates the resin and initiates the photopolymerization process. Historically, this light engine was a UV laser with relatively simple optical properties including low divergence, narrow spectral bandwidth, and fixed wavelength – spatial extent of the photopolymerization was controlled by rastering the focused beam across the build plate. More recently, digital micromirror device (DMD) and liquid crystal display (LCD) based light engines have been developed which expose the resin in a parallel fashion by controlling the exposure in a 2-dimensional pixelated manner. These more recent light engine designs tend to rely upon light emitting diodes (LEDs) as the photon source and these have more complex properties including high divergence (i.e. Lambertian emitter), broad spectral bandwidth, and less well-defined wavelength. Many printer manufacturers have developed multi-emitter light engine designs that compound these characteristics. As VP manufacturing continues to mature, the reproducibility of parts, both in terms of dimensional and functional properties, is becoming more and more critical. Here, we present our work on characterizing existing VP printer light engines. We show the types of heterogeneity that are present in these light engines and how they can directly impact printed parts. This then leads us to a discussion about what optical properties are important to control in VP light engines for improved print reproducibility. Finally, we discuss our latest efforts to develop a fully calibrated and characterized uniform light engine for performing careful photopolymerization studies that inform on the underlying photopolymerization physics without convolving light engine heterogeneity with the underlying photophysics. Figure 1

Engineering Super‐Poissonian Photon Statistics of Spatial Light Modes

AbstractThe nature of light sources is defined by the statistical fluctuations of the electromagnetic field. As such, the photon statistics of light sources are typically associated with distinct emitters. Here, the possibility of producing light beams with various photon statistics through the spatial modulation of coherent light is demonstrated. This is achieved by the sequential encoding of controllable Kolmogorov phase screens in a digital micromirror device. Interestingly, the flexibility of this scheme allows for the shaping of spatial light modes with engineered photon statistics at different spatial positions. The performance of this scheme is assessed through the photon‐number‐resolving characterization of different families of spatial light modes with engineered photon statistics. It is believed that the possibility of controlling the photon fluctuations of the light field at arbitrary spatial locations has important implications for quantum spectroscopy, sensing, and imaging.

Fourier Single-Pixel Imaging Based on Online Modulation Pattern Binarization

Down-sampling Fourier single-pixel imaging is typically achieved by truncating the Fourier spectrum, where exclusively the low-frequency Fourier coefficients are extracted while discarding the high-frequency components. However, the truncation of the Fourier spectrum can lead to an undesired ringing effect in the reconstructed result. Moreover, the original Fourier single-pixel imaging necessitated grayscale Fourier basis patterns for illumination. This requirement limits imaging speed because digital micromirror devices (DMDs) generate grayscale patterns at a lower refresh rate. In order to solve the above problem, a fast and high-quality Fourier single-pixel imaging reconstruction method is proposed in the paper. In the method, the threshold binarization of the Fourier base pattern is performed online to improve the DMD refresh rate, and the reconstruction quality of Fourier single-pixel imaging at a low-sampling rate is improved by generating an adversarial network. This method enables fast reconstruction of target images with higher quality despite low-sampling rates. Compared with conventional Fourier single-pixel imaging, numerical simulation and experimentation demonstrate the effectiveness of the proposed method. Notably, this method is particularly significant for fast Fourier single-pixel imaging applications.

Entangled optical quantum imaging method based on adaptive block compressed sampling

In the process of entangled optical quantum imaging, the Digital Micromirror Device (DMD) sampling mode affects imaging efficiency, and in the process of image sparse reconstruction, the use of a fixed sampling matrix affects the quality of image reconstruction. In this circumstance, this paper proposes an entangled optical quantum imaging method based on Adaptive Block Compressed Sampling with Two-Dimensional Information Entropy (ABCS-2DIE), which measures the texture details of the image through the two-dimensional information entropy of the image, adaptively allocates the sampling rate for each image block according to the texture distribution of the image, and designs the corresponding sampling matrix to sparsely sample the reference light. In addition, coincidence counting between the reference and signal light is considered in the reconstruction algorithm to obtain the target image. Experimental results show that compared with the Overall Compressive Sampling (OCS) method, the proposed method greatly shortens the imaging time and significantly improves the imaging quality. Besides, compared with the Fixed Block Compressed Sampling (FBCS) method, the image obtained by the proposed method has obvious improvement in visual effect, and the corresponding Peak Signal-to-Noise Ratio (PSNR) is improved by 2–4 dB with a slight increase in computation complexity. In all, the proposed method can make good use of the texture features of the image, effectively improving the quality of quantum imaging while reducing the imaging time.

Modulate scattered light field with Point Guard Algorithm

Speed and quality of wavefront shaping (WFS) are considered to be two major challenges in anti-scattering optical information transmission. Confronted with this, a novel optimization approach, namely Point Guard algorithm (PGA), is proposed based on the movement strategies of Point Guard (PG) in professional basketball association. The PGA manipulates the optical interference by encoding the digital micromirror device (DMD). The performance of the PGA can only be affected by one parameter (boundary value, BV), and the strategy of self-adaptive updating is adopted for this parameter to accelerate the speed of searching optimal pattern. Compared with the most popular WFS method genetic algorithm (GA), the PGA improves the speed and peak-to-background ratio (PBR) of single-point focusing by a factor of 10.49 and 4.05 within 500 iterations. We also accomplish 7-point focusing and form a bright and uniform Z-shape pattern in a short optimization period. Furthermore, it is demonstrated that the PGA can quickly reconstruct the visible image information through the scattering medium. With the ability to uniquely identify its target area, the reconstructed image ensures the secure optical communication. We also experimentally demonstrate that the PGA can parallel reconstruct three images in a short optimization period without obvious cross-talk. This new method has good potential in applications such as optogenetics, optical trapping and optical information transmission in complex environment.

Controlling the transmission of broadband light through scattering media using a digital micromirror device.

Wavefront shaping has emerged as a valuable technique in complex photonics, wherein the various eigenmodes of the disordered medium are selectively excited to control the overall transmission through the medium. The process utilizes active optical devices such as liquid crystal-based spatial light modulators (LC-SLM), deformable mirrors (DM), and digital micromirror devices (DMD). Among these, the latter is preferred for imaging through dynamic scattering media such as living biological tissues due to their high-speed refresh rate and increased resolution. This study employs a genetic algorithm along with binary amplitude modulation generated by a digital micromirror device to spatially and spectrally control the large spectral bandwidth through a scattering medium. We illustrate spatial single-point focusing of broadband light, multipoint focusing of broadband light, and programmable spectral filtering of the same through disordered samples.

Compressive Single-Pixel Read-Out of Single-Photon Quantum Walks on a Polymer Photonic Chip

Quantum photonic devices operating in the single photon regime require the detection and characterization of quantum states of light. Chip-scale, waveguide-based devices are a key enabling technology for increasing the scale and complexity of such systems. Collecting single photons from multiple outputs at the end-face of such a chip is a core task that is frequently non-trivial, especially when output ports are densely spaced. We demonstrate a novel, inexpensive method to efficiently image and route individual output modes of a polymer photonic chip, where single photons undergo a quantum walk. The method makes use of single-pixel imaging (SPI) with a digital micromirror device (DMD). By implementing a series of masks on the DMD and collecting the reflected signal into single-photon detectors, the spatial distribution of the single photons can be reconstructed with high accuracy. We also demonstrate the feasibility of optimization strategies based on compressive sensing.

Bi-frequency operation in a membrane external-cavity surface-emitting laser.

We report on the achievement of continuous wave bi-frequency operation in a membrane external-cavity surface-emitting laser (MECSEL), which is optically pumped with up to 4 W of 808 nm pump light. The presence of spatially specific loss of the intra-cavity high reflectivity mirror allows loss to be controlled on certain transverse cavity modes. The regions of spatially specific loss are defined through the removal of Bragg layers from the surface of the cavity high reflectivity mirror in the form of crosshair patterns with undamaged central regions, which are created using a laser ablation system incorporating a digital micromirror device (DMD). By aligning the laser cavity mode with the geometric centre of the loss patterns, the laser simultaneously operated on two Hermite-Gaussian spatial modes: the fundamental HG00 and the higher order HG11 mode. We demonstrate bi-frequency operation over a range of pump powers and sizes of spatial loss features, with a wavelength separation of approximately 5 nm centred at 1005 nm.

Anti-scattering optical information transmission based on iterative wavefront shaping in perturbation environment

Improving the quality of wavefront shaping (WFS) is a major problem of anti-scattering optical information transmission in the perturbation environment. To tackle this issue, we propose a simple and robust method, named Point Guard algorithm (PGA), to manipulate the optical interference by encoding the digital micromirror device (DMD). The PGA method is inspired by the movement strategies of Point Guard (PG) in professional basketball association. Compared with the most popular method genetic algorithm (GA), the proposed PGA method has a stronger anti-perturbation capacity. In the experiment, the scattering medium consists of ground glass and polystyrene microspheres (PS) suspended in deionized water, and the movement of microspheres is used to cause a perturbation. It is found that PGA still has a better modulation quality when the suspension is too thick to see the ballistic light. PGA puts a new perspective in applications such as optogenetics and biomedical imaging in complex environment.

Enhancing Focusing and Defocusing Capabilities with a Dynamically Reconfigurable Metalens Utilizing Sb2Se3 Phase-Change Material.

Metalenses are emerging as an alternative to digital micromirror devices (DMDs), with the advantages of compactness and flexibility. The exploration of metalenses has ignited enthusiasm among optical engineers, positioning them as the forthcoming frontier in technology. In this paper, we advocate for the implementation of the phase-change material, Sb2Se3, capable of providing swift, reversible, non-volatile focusing and defocusing within the 1550 nm telecom spectrum. The lens, equipped with a robust ITO microheater, offers unparalleled functionality and constitutes a significant step toward dynamic metalenses that can be integrated with beamforming applications. After a meticulously conducted microfabrication process, we showcase a device capable of rapid tuning (0.1 MHz level) for metalens focusing and defocusing at C band communication, achieved by alternating the PCM state between the amorphous and crystalline states. The findings from the experiment show that the device has a high contrast ratio for switching of 28.7 dB.

Multimodal high-resolution retinal imaging using a camera-based DMD-integrated adaptive optics flood-illumination ophthalmoscope.

We demonstrate the feasibility of a multimodal adaptive optics flood-illumination ophthalmoscope, able to provide both bright-field and dark-field images (such as phase contrast). The multimodality was made possible by integrating a digital micromirror device (DMD) at the illumination path to project a sequence of complementary high-resolution patterns into the retina. Through a versatile post-processing method that digitally selects backscattered or multiply scattered photons, we were able: (1) to achieve up to four-fold contrast increase of bright-field images when imaging the photoreceptor mosaic and nerve fibers; and (2) to visualize translucent retinal features such as capillaries, red blood cells, vessel walls, ganglion cells, and photoreceptor inner segments through phase contrast.

Beam‐Steering Metadevices for Intelligent Optical Wireless‐Broadcasting Communications

High‐performance beam‐steering devices play a crucial role for optical wireless communication (OWC), which can meet the demand for increasing number of wireless mobile devices and emerging high‐speed multimedia applications. Conventional beam‐steering optical components like spatial light modulator and digital micromirror device are limited to realize a small steering angle (typ. several degrees), thus dramatically limits the spatial scope of OWC. Herein, a beam‐steering metadevice utilizing an ultracompact metasurface assisted with a spatial light modulator is presented, which can significantly increase the beam‐steering angle without at the cost of complicated optical setup like conventionally used angle magnifier. Based on the actively tunable beam‐steering metadevice, an intelligent bidirectional optical broadcasting communication system is designed and experimentally demonstrated, which exhibits nine broadcasting areas covering a large field‐of‐view of 20° × 20°, with user‐defined dynamic beam‐steering ability in each area, and each user has a data rate of 10 Gbps for both upstream and downstream transmission. The proposed metadevices can meet the demand of intelligent optical wireless communication which requires both high‐performance and low‐cost for practical purpose, under currently available technical architectures.

DMD-based compact SIM system with hexagonal-lattice-structured illumination.

In this study, we developed a novel, compact, and efficient structured illumination microscopy (SIM) system, to our best knowledge. A binary hexagonal lattice pattern was designed and implemented on a digital micromirror device (DMD), resulting in a projection-based structured-light generation. By leveraging the combination of the high-speed switching capability of the DMD with a high-speed CMOS camera, the system can capture 1024×1024 pixels images at a 200fps frame rate when provided with sufficient illumination power. The loading of the hexagonal lattice pattern reduces the number of images required for reconstruction to seven, and by utilizing the DMD modulating characteristics on the illumination path, there is no need to use bulky mechanical structures for phase shifting. We designed a compact system with 110m m×150m m×170m m dimensions that displayed a 1.61 resolution enhancement for fluorescent particle and biological sample imaging.

Genetic algorithm-based optical proximity correction for DMD maskless lithography.

We present an optical proximity correction (OPC) method based on a genetic algorithm for reducing the optical proximity effect-induced pattern distortion in digital micromirror device (DMD) maskless lithography. Via this algorithm-assisted grayscale modulation of the initial mask at the pixel level, the exposure pattern can be enhanced significantly. Actual exposure experiments revealed that the rate of matching between the final exposure pattern and the mask pattern can be increased by up to 20%. This method's applicability to complex masks further demonstrates its universality for mask pattern optimization. We believe that our algorithm-assisted OPC could be highly helpful for high-fidelity and efficient DMD maskless lithography for microfabrication.

Coded aperture compression temporal imaging based on a dual-mask and deep denoiser.

Coded aperture compressive temporal imaging (CACTI) is the mapping of multiple frames using different encoding patterns into a single measurement and then using an algorithm to reconstruct the required high-dimensional signals, thus enabling high-speed photography on low-speed cameras. An encoding pattern and a reconstruction algorithm both play a critical role for CACTI. To improve the quality of the reconstruction, in terms of encoding, we took advantage of the reflective properties of the digital micromirror device and used a complementary dual-mask pattern to obtain more projection information. In terms of decoding, we developed what we believe, to the best of our knowledge, is a new model combining the weighted Landweber regularization with the relaxation strategy and a deep denoiser. The experimental results show the superiority of our proposed encoding-decoding combination, which achieves better performance in terms of the peak SNR, structural similarity index measure, and visual effects.