Photonics Industry Research Articles

59‐1: Invited Paper: From Lab to Fab: Challenges and Requirements for High‐Volume MicroLED Manufacturing Equipment

Availability of standard, high volume production tools and processes enabled the commercialization and commoditization of LCD and OLED. For microLED, the lack of processes standards and the proliferation of technology paths hinders the development of high‐volume manufacturing tools. This paper discusses the challenges for equipment manufacturers attempting to capture the microLED opportunity. While various technology bottlenecks remain, the microLED display industry can leverage on existing expertise and equipment from the display, semiconductor, LED and photonic industries to accelerate industrialization.

Microwave Pioneers: Kam Lau, “μWaves Meet Photons”

This article is part of a continuing series of biographical pieces on persons who have made significant and continuous contributions to microwave science, technology, and applications over the course of their careers. It is intended to bring to the reader, especially those new to the field, a portrait of an individual who serves as a role model for the community and a detailed description of their accomplishments. At the same time, it tries to bridge with commonality, the experiences of the subject with those of the scientists, engineers and technologists who are following in their footsteps or hope to establish a similar record of success. The articles are composed only after an extensive face-to-face interview with the subject and are helped immensely by additional input and editing by the subjects themselves. The focus of this article is Professor Kam-Yin Lau, who developed the first photonic source capable of high-fidelity optical modulation at 10 GHz and beyond, and successfully introduced photonics into the traditional microwave disciplines. His work during the 1980s enabled hitherto unattainable long-distant (∼50 km) guided transport of microwave signals over optical fibers. These accomplishments helped spur the microwave photonics industry that has transformed both wired and wireless communications networks, and as you will read, several other applications of national and scientific significance. It is appropriate that Professor Lau is the recipient of this year's Microwave Theory and Techniques Society's Microwave Pioneer award for his development and commercialization of RoF (RF-over-Fiber) which launched the microwave photonics industry. As both an industry pioneer and an academic, Professor Lau's accomplishments fit well within the scope of this series. I hope you will both enjoy and learn from his account of where he came from, what motivated his career choices, and the many notable people he interacted with.

Study of Refractive Index and Birefringence Variation near the Surface of LiNbO3 Open Type Optical Waveguide using Point Dipole Approximation

In view of the immense use of LiNbO3 (LN) in the Photonic industry, a need arises to develop a theory to study the variation of Refractive Indices near the surface of LN device. The “Local” fields as experienced by ions on or near the surface of a dielectric medium ought to be different from those in the interior, thus one expects a Refractive Index variation near the surface of the material. In the studies involving thin films and optical waveguides, this variation could possibly alter the propagation characteristics. The variation of ordinary and extraordinary refractive indices (no, ne) from the surface to the interior of depth 69.315A° near the surface for X-cut and Z-cut LN waveguides are evaluated using theoretical Point Dipole Approximation (PDA) method. For an X-cut waveguide, no is found to decrease from 2.9696 on the surface to 2.2864 in the interior whereas, ne is found to increase from 1.4849 to 2.2024. The birefringence (dn=ne–no) is negative and observed to be increase from -1.4847 to -0.0840. For a Z-cut waveguide, no is found to increase from 1.8046 to 2.2864 whereas ne is found to decrease from 2.7005 to 2.2024. Here the birefringence is positive, decreasing from 0.8958 to zero to a depth of 60.5A° and further decreasing to -0.0840 to a depth of 69.315A°. It is observed that the variation of refractive indices no , ne and dn variation with depth near the surface for both the cases are quite opposite in nature. This is primarily due to the dipole orientation and their relative distributions in the lattice being different for the two directions of the electric vectors of light as is evident from the values.

The Effects of Technological Progress of the Domestic Photonics Industry on Imports and Exports of Related Industries

The Effects of Technological Progress of the Domestic Photonics Industry on Imports and Exports of Related Industries

Boron carbide nanowires from castor oil for optronic applications: a low‐temperature greener approach

The development of one-dimensional nanostructures has revolutionized electronic and photonic industries because of their unique properties. The present paper reports the low-temperature green synthesis of boron carbide nanowires, of diameter 14 nm and length 2 µm, by the condensation method using castor oil as the carbon precursor. The nanowires synthesized exhibit beaded chain morphology, and bandgap energy of 2.08 eV revealed through the Tauc plot analysis. The structure of boron carbide nanowires is revealed by micro-Raman, Fourier transform infrared spectroscopic, and X-ray diffraction analyses. The thermogravimetric analysis of the sample reveals the excellent thermal stability. The photoluminescence study reveals the nanowire’s blue light emission capability under ultraviolet excitation, which is substantiated by the CIE plot suggesting its potential in photonic applications.

Innovation and SMEs patent propensity in Korea

This paper analyzes the patent propensity as an outcome of innovative activities of regional SMEs. To achieve the aims, we apply robust regression analysis to estimate the models to test 5 research hypotheses using 263 firm level data located at Gwangju region in Korea. Our empirical results show that a firm's industry characteristics, such as machinery and automotive parts industry, is negatively related with propensity to patent innovation. Also, unlike expectations, the InnoBiz firms designated as innovative SMEs by the government are not performing differently than general firms. Only the CEO's academic credentials are positively related with propensity to patent. From the findings, we can conclude that patenting propensity is not directly related with a firm's characteristics but mainly to CEO's managerial strategy. Also, we cannot find evidence for policy effectiveness from public support given to InnoBiz firms as part of the state policy to nurture photonic industry to boost regional economic development. Given the lack of strong policy effects, a new industry policy should be considered to actively promote SMEs innovativeness.

Laser Thermochemical High-Contrast Recording on Thin Metal Films.

Laser-induced thermochemical recording of nano- and microsized structures on thin films has attracted intense interest over the last few decades due to essential applications in the photonics industry. Nevertheless, the relationship between the laser parameters and the properties of the formed oxide structures, both geometrical and optical, is still implicit. In this work, direct laser interference patterning of the titanium (Ti) film in the oxidative regime was applied to form submicron periodical structures. Depending on the number of laser pulses, the regime of high contrast structures recording was observed with the maximum achievable thickness of the oxide layer. The investigation revealed high transmittance of the formed oxide layers, i.e., the contrast of recorded structures reached up to 90% in the visible range. To analyze the experimental results obtained, a theoretical model was developed based on calculations of the oxide formation dynamics. The model operates on Wagner oxidation law and the corresponding optical properties of the oxide–metal–glass substrate system changing nonlinearly after each pulse. A good agreement of the experimental results with the modeling estimations allowed us to extend the model application to other metals, specifically to those with optically transparent oxides, such as zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), and tantalum (Ta). The performed analysis highlighted the importance of choosing the correct laser parameters due to the complexity and nonlinearity of optical, thermal, and chemical processes in the metal film during its laser-induced oxidation in the air. The developed model allowed selecting the suitable temporal–energetic regimes and predicting the optical characteristics of the structures formed with an accuracy of 10%. The results are promising in terms of their implementation in the photonics industry for the production of optical converters.

L-band femtosecond fiber laser based on a reduced graphene oxide polymer composite saturable absorber

We demonstrate an L-band passively mode-locked erbium-doped fiber laser emitting at 1599.43 nm wavelength at a pulse train of 5.68 MHz. The microfiber reduced graphene oxide composite behaves as a saturable absorber that was fabricated using in-situ wet chemical and dip-coating methods. During operation, a single-pulse soliton was observed at a mode-locking threshold of 40 mW. This is a few times lower than most of the previous assessments in the same class of wavelength band and graphene saturable absorbers. The pulse duration was 568 fs with a maximum average output power of 6.75 mW. In addition, the superiority of this simple fabrication method facilitates its potential of mass production for applications in ultrafast photonics industries.

Advances in on-chip photonic devices based on lithium niobate on insulator

Crystalline lithium niobate (LN) is an important optical material because of its broad transmission window that spans from ultraviolet to mid-infrared and its large nonlinear and electro-optic coefficients. Furthermore, the recent development and commercialization of LN-on-insulator (LNOI) technology has opened an avenue for the realization of integrated on-chip photonic devices with unprecedented performances in terms of propagation loss, optical nonlinearity, and electro-optic tunability. This review begins with a brief introduction of the history and current status of LNOI photonics. We then discuss the fabrication techniques of LNOI-based photonic structures and devices. The recent revolution in the LN photonic industry has been sparked and is still being powered by innovations of the nanofabrication technology of LNOI, which enables the production of building block structures, such as optical microresonators and waveguides of unprecedented optical qualities. The following sections present various on-chip LNOI devices categorized into nonlinear photonic and electro-optic tunable devices and photonic-integrated circuits. Some conclusions and future perspectives are provided.

(Invited) Temperature Stable III-V/Si/Si3N4 Heterogeneous Integrated Laser

Silicon nitride (Si3N4) is a widely used complementary metal–oxide–semiconductor (CMOS) compatible material in modern IC industry and recent years have witnessed tremendous development of Si3N4 in photonics. The benefits of Si3N4 in photonics include low loss, low thermo optic coefficient and negligible nonlinear absorption at telecom wavelengths. Devices based on Si3N4 waveguides innovates in the field of nonlinear photonics, sensing, microwave photonics and so on. However, they are all dependent on the excellent passive properties of Si3N4. There are no successful demonstrations of fully integrated laser with Si3N4 yet.For an external cavity laser design, it is beneficial to have a low loss waveguide. A low loss waveguide platform can enable a long optical cavity which can greatly reduce the laser phase noise. Butt-coupled hybrid integrated lasers are extensively studied using Si3N4 cavity, but they are based on separate chips and are not scalable for large volume integration.Heterogeneous integration of III-V material and Si has achieved great success in the past years, offering the silicon photonics industry with low-cost, high-performance silicon photonic integrated circuits fully integrated with lasers. For the heterogeneous integration of III-V material with Si3N4, the biggest challenge is the large index mismatch. Typical III-V epi used for heterogeneous lasers is about 2 μm thick and extreme tapering cannot facilitate a high coupling efficiency between the III-V layer and Si3N4 layer.In this work, we used an intermediate Si layer to bridge the index mismatch between the III-V and Si3N4 layer. By using multilayer heterogeneous integration shown in Fig.1 (a), we enable a III-V/Si/Si3N4 structure to efficiently couple the mode between III-V/Si and Si/Si3N4. Based on this structure, we designed the III-V/Si/Si3N4 laser using an external Si3N4 spiral grating as the feedback cavity. This spiral grating provides the narrow-band optical feedback and determines the laser wavelength. The laser configuration is shown in Fig. 1(b).The laser performance is summarized in Fig. 1 (c)-(e). The lasing wavelength is at 1546 nm and the laser has over 58 dB side mode suppression ratio (SMSR). This shows the excellent mode selectivity from the 20 mm long Si3N4 spiral grating. We measured the frequency noise of the laser. With optimized loop mirror reflectivity, the laser fundamental linewidth is about 4 KHz. This linewidth can be further improved by lowering the Si3N4 waveguide loss. We anticipate the laser fundamental linewidth can be reduced to below 100 Hz using this design.Another advantage of integrating Si3N4 into the laser cavity is to have much higher temperature stability. By comparison, III-V/Si/Si3N4 laser wavelength shifts by only 0.47 nm for 45 oC change, while for a III-V/Si DBR laser this wavelength shift is 3.3 nm. This is over 7x difference and is a result of the low thermo-optic coefficient of Si3N4. When combined with Si3N4 based arrayed waveguide gratings, our laser can be potentially used in dense wavelength-division-multiplexing (DWDM) systems.The successful demonstration of this multilayer heterogeneous integration will enable a whole new class of devices that require low loss waveguides and are presently not integrated. This is a key step in fully exploiting the capabilities of wafer-bonding technologies. We anticipate this platform can take narrow-linewidth semiconductor laser performance to a new level. Figure 1

Investigation on key properties of solution grown l-Leucine hydrobromide single crystal: A semi-organic NLO material

Good quality single crystals of l-Leucine hydrobromide, a prominent NLO material, have been grown successfully by conventional slow evaporation solution technique to meet the requirement of photonics industry. To confirm the identity of the synthesized material and the % composition of constituent element CHN analysis was carried out. HRXRD rocking curve confirms the better crystalline perfection as it has single sharp peak with FWHM 17.59 arc sec and almost uniform on both sides. Thermal properties were investigated by DSC and photo-acoustic anlaysis. Thermal diffusivity, conductivity and effusivity have been calculated from photo-acoustic analysis. Some electronic parameters of technical importance were also calculated by Clausius- Mossotti relation. Mechanical behavior has been examined by employing nano-indentation technique. Several useful mechanical properties like hardness, stiffness, Young's modulus were studied and found that both hardness and Young's modulus depends upon the peak load.

Estimation of maximum temperature and thermal crosstalk between two active elements in a PIC: development of a thermal equivalent circuit.

The operating temperature plays a key role in the performance and lifetime of photonic integrated circuits (PICs). Miniaturization and increasing heat dissipation promote thermal crosstalk effects and pose additional challenges to the PIC designer. The European Photonics Industry Consortium recommends thermal modeling during design phase. However, a fully numerical optimization of a particular layout requires an unrealistically large number of simulations. Here, we propose a compromise approach: a set of carefully chosen simulations are performed with a multi-physics software. The obtained results are used to derive a linearized equivalent thermal circuit that can be used to maximize the power levels and to minimize the distance between the chosen components while guaranteeing the absence of a thermal crosstalk. For simplification, this model is derived considering a PIC with only two active components. Other parameters are varied, such as the material of the holder (silicon or diamond) and the layer of epoxy that is used to attach the PIC to the holder. The obtained circuit is used to determine the maximum dissipated power or the minimum distance between the components while keeping some predetermined specifications. The model can be extended to contain more elements or to include transient analysis of the temperature distribution.

Erbium-doped hybrid waveguide amplifiers with net optical gain on a fully industrial 300 mm silicon nitride photonic platform.

Recently, erbium-doped integrated waveguide devices have been extensively studied as a CMOS-compatible and stable solution for optical amplification and lasing on the silicon photonic platform. However, erbium-doped waveguide technology still remains relatively immature when it comes to the production of competitive building blocks for the silicon photonics industry. Therefore, further progress is critical in this field to answer the industry's demand for infrared active materials that are not only CMOS-compatible and efficient, but also inexpensive and scalable in terms of large volume production. In this work, we present a novel and simple fabrication method to form cost-effective erbium-doped waveguide amplifiers on silicon. With a single and straightforward active layer deposition, we convert passive silicon nitride strip waveguide channels on a fully industrial 300 mm photonic platform into active waveguide amplifiers. We show net optical gain over sub-cm long waveguide channels that also include grating couplers and mode transition tapers, ultimately demonstrating tremendous progress in developing cost-effective active building blocks on the silicon photonic platform.

Primer on silicon neuromorphic photonic processors: architecture and compiler

AbstractMicroelectronic computers have encountered challenges in meeting all of today’s demands for information processing. Meeting these demands will require the development of unconventional computers employing alternative processing models and new device physics. Neural network models have come to dominate modern machine learning algorithms, and specialized electronic hardware has been developed to implement them more efficiently. A silicon photonic integration industry promises to bring manufacturing ecosystems normally reserved for microelectronics to photonics. Photonic devices have already found simple analog signal processing niches where electronics cannot provide sufficient bandwidth and reconfigurability. In order to solve more complex information processing problems, they will have to adopt a processing model that generalizes and scales.Neuromorphic photonicsaims to map physical models of optoelectronic systems to abstract models of neural networks. It represents a new opportunity for machine information processing on sub-nanosecond timescales, with application to mathematical programming, intelligent radio frequency signal processing, and real-time control. The strategy of neuromorphic engineering is to externalize the risk of developing computational theory alongside hardware. The strategy of remaining compatible with silicon photonics externalizes the risk of platform development. In this perspective article, we provide a rationale for a neuromorphic photonics processor, envisioning its architecture and a compiler. We also discuss how it can be interfaced with a general purpose computer, i.e. a CPU, as a coprocessor to target specific applications. This paper is intended for a wide audience and provides a roadmap for expanding research in the direction of transforming neuromorphic photonics into a viable and useful candidate for accelerating neuromorphic computing.

1.3 µm Quantum Dot‐Distributed Feedback Lasers Directly Grown on (001) Si

AbstractDistributed feedback (DFB) lasers represent a central focus for wavelength‐division‐multiplexing‐based transceivers in metropolitan networks. Here, the first 1.3 µm quantum dot (QD) DFB lasers grown on a complementary metal‐oxide‐semiconductor (CMOS)‐compatible (001) Si substrate are reported. Temperature‐stable, single‐longitudinal‐mode operation is achieved with a side‐mode suppression ratio of more than 50 dB and a threshold current density of 440 A cm−2. A single‐lane rate of 128 Gbit s−1 with a net spectral efficiency of 1.67 bits−1 Hz−1 is demonstrated, with an aggregate total transmission capacity of 640 Gbit s−1 using five channels in the O‐band. Apart from the QD active region growth, the overall fabrication is essentially identical to the commercial process for quantum well (QW) DFB lasers. This provides a process‐compatible path for QD technology into commercial applications previously filled by QW devices. In addition, the capability to grow laser epi across entire CMOS‐compatible (001) Si wafers adds extra benefits of reduced cost, improved heat dissipation, and manufacturing scalability. Through direct epitaxial integration of III–Vs and Si, one can envision a revolution of the photonics industry in the same way that CMOS design and processing revolutionize the microelectronics industry. This is discussed from a system perspective for on‐chip optical interconnects.

Fringe field effect free high-resolution display and photonic devices using deformed helix ferroelectric liquid crystal

ABSTRACT The fringe field effect (FFE) is one of the biggest bottlenecks for the display, and the photonic industry limiting the pixel per inch (PPI) to ~450. The modern applications such as AR/VR headsets and photonic elements such as wavelength selective switches required significantly higher PPI panel. Despite the rigorous research efforts, conventional LCs still show serious FFE, and therefore, hinder the progress of high PPI display and photonic elements. In this article, we studied FFE in the deformed helix ferroelectric liquid crystals (DHFLCs) and found that the subwavelength pitch of the DHFLCs is critically important to suppress the FFE. These DHFLCs show no FFE, for the electric field parallel to the FLC helix, however, we have observed some FFE for the electric field perpendicular to the FLC helix. Additionally, we have found that the high-frequency driving further suppresses the FFE. Later, we deployed DHFLCs to diffraction grating and display to confirm our findings. The proposed DHFLCs with subwavelength pitch can support pixel density up to 4233 PPI for displays, and up to 12,700 PPI for monochromatic photonic devices. Thus, the fast switchable DHFLCs with subwavelength pitch pave the way for the high-pixel density display and photonic devices.

Multifunctional polyimides by direct silyl ether reaction of pendant hydroxy groups: Toward low dielectric constant, high optical transparency and fluorescence

Unsatisfied overall properties and high-cost production are major obstacles for the commercialization of polyimide (PI) films. This work aims to develop a convenient way with low cost to prepare multifunctional PI films with excellent combined properties of low dielectric constant (k), high transparence and fluorescence by the direct structural modification on easily available PIs containing active groups. Thus, a series of fluorene-based PIs with tert-butyldimethylsiloxy (TBS) side groups (PI-TBSs) were successfully synthesized by a direct silyl ether reaction of hydroxyl-containing PIs (PI-OHs) with tert-butyldimethylsilyl chloride (TBSCl). The resulted PI-TBSs with high yield are readily soluble in many common solvents, even in low-boiling-point solvents at room temperature. Due to the presence of the cardo-type fluorene structure, PI-TBS films still possess the excellent thermal properties with a glass transition temperature (Tg) of 311.2–338.9 °C and a 5% weight loss temperature (T5%) of 469.5–506.4 °C in N2 and the good mechanical properties with a tensile strength (TS) of 57.7–79.1 MPa. In addition, PI-TBS films exhibit the light color with the high optical transparence (over 80% at 450 nm), the low dielectric constant (as low as 2.44 at 1 MHz for PI-TBS-2F) and the bright fluorescence because of the reduced charge transfer (CT) interaction in PI chains chemically bonded by bulky non-polar TBS groups. As the result, this work provides a convenient way to prepare multifunctional PI films with the excellent overall properties, which show high potential applications of these PI films in microelectronic, electric and photonics industries.

Generation of UV Signal using 1D Photonic Structure: A Proposal to Photonic Industry for Designing Laser Torch

Ultraviolet (UV) signal pertaining to the visible spectrum is generated here using silicon based 1D photonic structure. Here optical band gap analysis is a basic principle of the same. Moreover the proposed structure operates with the absorption loss of the signal, which is found to be zero with reference to the input signal. The outcomes of the present paper deals with the generation of the Ultraviolet Signal of 240 nm to 280 nm, which is useful for killing of germs in the water. Further such signal could be used in the water purification. Finally, a schematic diagram for the realisation of Laser Torch is proposed which could be designed at the industry level to understand in its physical form.

Review of Recent Progress on Silicon Nitride-Based Photonic Integrated Circuits

Silicon photonic devices used in the photonics industry over the past three decades have helped in realizing large-scale photonic integrated circuits. Silicon nitride (Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) is another CMOS-compatible platform that provides several advantages such as low loss, high optical power tolerance, and broad spectral operation band from visible to infrared wavelengths. Recently, the combination of Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> waveguide technology with silicon photonics and III-V materials has opened up new areas in on-chip applications. Researchers in the field are primarily focusing on its applications such as on-chip gas sensing, nonlinear optical signal processing, and label-free biosensors based on photonic integrated circuits. In this review paper, we discuss Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> material-based platforms for a variety of applications with devices ranging from passive to active and hybrid photonic devices.

Industry-Specific Makerspaces: Opportunities for Collaboration and Open Innovation

The rise of the maker movement, including hackathons and fablabs, provides new opportunities for companies to boost innovation by collaborating with creative, tech-savvy and intrinsically motivated people, known as makers. This paper connects open innovation and maker movement research by investigating how makers and companies can work together within an industry-specific makerspace setting. We use a qualitative case study design and focus on the German photonics industry. Our results shed light on the expectations makers and companies have when considering a collaboration, along with the perceived benefits and risks. Furthermore, we uncover crucial design factors for industry-specific makerspaces.