Optical Generation Research Articles

Effect of annealing on ion-beam-sputtered hafnium oxide thin films properties

HfO2 films are high laser damage-threshold and low-absorption thin-films that can be utilized for a broad range of optoelectronic and optical applications. In this study, HfO2 thin films were prepared via dual ion beam sputtering followed by annealing in the atmosphere at temperatures ranging from 200 to 700 °C. The optical properties, microstructure, film stress, and absorption loss of the HfO2 films at various annealing temperatures were then systematically characterized. The results revealed that the properties of the films were improved after annealing at temperatures below 500 °C. Specifically, at an optimal annealing temperature of 400 °C, the residual stress of the films was minimized close to zero and the absorption loss was as low as 1 ppm. However, at annealing temperatures reaching 600 °C, the films began to crystallize, leading to the deterioration of their optical properties. Optimizing the process parameters for HfO2 thin film deposition is crucial for developing the next generation of high-performance laser optics.

Tunable microwave and optical frequency comb generator with the aid of cascaded MZM structure

Tunable microwave and optical frequency comb generator with the aid of cascaded MZM structure

Performance studies on group-velocity-matched femtosecond optical parametric generation

We present a comparative study and detailed characterization of high-power femtosecond optical parametric generation (OPG) at 10 MHz repetition rate in the near and mid-infrared by exploiting near-zero group-velocity-mismatch (GVM) in the nonlinear crystals of PPLN and MgO:PPLN. Using a microchip-started amplified Mamyshev fiber oscillator delivering 198 fs pulses at 1064 nm as the pump source and deploying 19-mm-long PPLN and 42-mm-long MgO:PPLN as gain media, we study in detail the influence of crystal length and pump pulse duration on femtosecond group-velocity-matched interaction in the OPG process. The OPG source is tunable across 1445–1577 nm in the signal and 3318–4412 nm in the idler, and can provide average output powers of up to 439 mW in the signal at 1530 nm and 197 mW in the idler at 3550 nm, at slope efficiencies of ∼50% and ∼20%, respectively. Signal pulses as short as 275 fs are obtained using the shorter crystal, while longer signal pulses with similar output powers are generated with the longer crystal. Experimental results are supported by theoretical simulations, providing good agreement. The OPG source exhibits excellent power stability with high spatial quality of M2<1.5 in the signal and idler beams.

Semiconductor optical amplifiers as an optical arbitrary waveform generator for high-energy laser systems

A simple and straightforward technique is presented as a novel temporally controllable front-end for nanosecond very-high energy laser systems. It is based on an original utilization of a semiconductor optical amplifier (SOA) used as an intensity modulator. The essential characteristics of the component are analyzed in order to evaluate potential limitations. Various parameters of interest for standard operation are displayed, demonstrating its usability and its effectiveness. We demonstrate arbitrary and controllable pulse temporal profiles with duration ranging from 1 nanosecond to 100 nanoseconds and a temporal precision of 1.1 ns. A high extinction ratio is also achieved ensuring a modulation contrast up to 53 dB. The SOA is then integrated into an existing operating system in an ultra-compact, reliable all-fibered system. It is used to seed a 2*200 J laser system, exhibiting excellent performance, and validating its usability under operation conditions without any detrimental effects.

A hybrid trans-modal liquid crystal optical vortex generator

This work experimentally validates a large-aperture optical vortex generator using a novel hybrid structure, combining transmission electrode and modal techniques, in what we term the trans-modal technique. The continuous transmission electrode is designed to generate a linear voltage distribution between the contact electrodes, while the electrode stubs distribute the voltage across the active area. A high-resistivity layer of the conducting polymer PEDOT fills the gap between the electrodes, resulting in a completely continuous voltage distribution. A 1-cm aperture device is experimentally demonstrated, but the structure is completely scalable. Theoretical results validate the design, and experimental results demonstrate precise control over the topological charge for both positive and negative values of orbital angular momentum. Remarkably, the conversion efficiency for the first topological charges is almost 100%. The reduction in efficiency of the higher-order modes has been explained theoretically, and it is not caused by design but by the PEDOT characteristics. The fabrication process is straightforward, as the high-resistivity layer may also be inhomogeneous. This work contributes significantly to the field by introducing a novel method for optical vortex generation. The simplicity of the fabrication process, high conversion efficiency, and ability to control the topological charge make this technique a promising avenue for future research and applications.

High signal-to-noise ratio optical frequency comb generation based on a Brillouin amplified recirculating frequency shifter loop

A novel approach to generate optical frequency combs (OFCs) with high signal-to-noise ratio (SNR) based on a Brillouin amplified recirculating frequency shifter loop (RFSL) is proposed and experimentally demonstrated. Different from the conventional RFSL-based OFC generator using an EDFA, a multi-channel Brillouin gain fiber is introduced in the scheme for optical power amplification to compensate for the optical losses inside the loop. The frequency positions of the Brillouin pump laser lines and their corresponding Brillouin gain profiles are precisely characterized by employing the laser scanning spectroscopy method. The SNR of the OFC is significantly enhanced from 12 dB to 30 dB. The proposed OFC generation with high-SNR performance plays an essential role in the development of optical communications and high-precision spectroscopy.

High-efficiency mid-infrared CW-seeded optical parametric generation in PPLN waveguide

Mid-infrared optical sources have been extensively used in a variety of applications, including gas sensing and metrology, by exploiting the fingerprint fundamental vibrational absorption bands of molecules in this spectral region. Parametric frequency conversion techniques, such as optical parametric generation (OPG) and optical parametric oscillator (OPO), represent common methodologies for mid-infrared generation. Notably, continuous-wave (CW)-seeded OPG exhibits superior stability and performance compared to conventional OPG. Here, we present a simple method for mid-infrared source generation based on femtosecond OPG in periodically poled lithium niobate (PPLN) waveguides. In addition to its robustness and simplicity, mid-infrared CW-seeded OPG features a high quantum conversion efficiency of 46.5% and a low threshold. The phase of CW-seeded OPG was passively referenced to the CW laser, making it suitable for dual-comb applications. This system shows great promise in the miniaturization of mid-infrared combs and will be applied to non-laboratory applications, including open-path atmospheric gas sensing and portable environmental monitoring.

Optical Pulse Generation with Programmable Positions in an Actively Mode-locked Optical Cavity

Optical Pulse Generation with Programmable Positions in an Actively Mode-locked Optical Cavity

An approach to generate cross-polarization modulation-enabled optical frequency comb with enhanced spectral flatness in traveling-wave semiconductor optical amplifiers

Abstract This paper proposes a method for generating an optical frequency comb (OFC) using the cross-polarization modulation (XPolM) effect in a traveling-wave semiconductor optical amplifier (TW-SOA). The TW-SOA acted as a lumped amplifier, enabling pulse generation within the comb. The proposed method of OFC generation achieved a comb spectrum with 51 lines and a maximum power deviation of 1.8 dB, indicating excellent spectral flatness. The proposed approach effectively utilized XPolM in a TW-SOA to create broad flat OFCs. The effectiveness of XPolM depends on various SOA parameters, such as pump and signal powers, and the confinement factor. To understand the XPolM-enabled OFC behavior, various parameters, such as input polarization, bias current, SOA confinement factor, and carrier density, have been optimized. These parameters significantly influenced the generated comb spectrum. This study also provides valuable insights into optimizing comb characteristics through theoretical analysis. The proposed OFC generation was simulated using an OptiSystem simulator. This has paved the way for the potential use of the comb as a multichannel source in various optical devices.

A Filterless Optical Generation Scheme of Frequency 32-Tupling Millimeter-Wave Signal Based on Cascaded Polarization Modulators

ABSTRACT In the work, a new method for generating a frequency 32-tupling millimeter-wave (mm-wave) signal with higher quality only using four polarization modulators (PolM) is proposed. To generate a pure 32-tupling mm-wave signal, it is necessary to beat ± 16th-order optical sidebands beat frequency. Mathematical calculations and simulation results both show that the scheme can obtain ± 16th-order harmonics, thereby generating frequency 32-tupling mm-wave signals. The optical sideband suppression ratio (OSSR) and radio frequency spurious suppression ratio (RFSSR) can reach 53.74 dB and 47.59 dB, respectively. Besides, the parameters that will affect OSSR and RFSSR are also analyzed and acceptable error ranges are provided.

Photonic modes prediction via multi-modal diffusion model

Abstract The concept of photonic modes is the cornerstone in optics and photonics, which can describe the propagation of the light. The Maxwell's equations play the role in calculating the mode field based on the structure information, while this process needs a great deal of computations, especially in the handle with a three-dimensional model. To overcome this obstacle, we introduce the Multi-Modal Diffusion model to predict the photonic modes in one certain structure. The Contrastive Language–Image Pre-training (CLIP) model is used to build the connections between photonic structures and the corresponding modes. Then we exemplify Stable Diffusion (SD) model to realize the function of optical fields generation from structure information. Our work introduces Multi-Modal deep learning to construct complex mapping between structural information and light field as high-dimensional vectors, and generates light field images based on this mapping.

Quantum dot fourth-harmonic colliding pulse mode-locked laser for high-power optical comb generation

Quantum-dot mode-locked lasers have advantages such as high temperature stability, large optical bandwidth, and low power consumption, which make them ideal optical comb sources, especially for wavelength-division multiplexing (WDM) telecommunications, and optical I/O applications. In this work, we demonstrate an O-band quantum dot colliding pulse mode-locked laser (QD-CPML) to generate optical frequency combs with 200 GHz spacing with maximum channels of 12 within 3 dB optical bandwidth. To achieve the high output power of individual comb lines, four channel conditions are implemented at central wavelength of 1310 nm for WDM transmission experiments. Each channel exhibits more than 10 dBm output power with 200 Gb/s PAM-4 and 270 Gb/s PAM-8 modulation capability via thin-film LiNbO3 Mach–Zehnder interferometer modulator without the requirement of any optical amplifications. This high-order QD-CPML is an ideal comb source for power-efficient optical interconnects and large bandwidth optical data transmission.

Evaluation of TOPAS MC tool performance in optical photon transport and radioluminescence-based dosimetry

Radiation therapy plays a pivotal role in modern cancer treatment, demanding precise and accurate dose delivery to tumor sites while minimizing harm to surrounding healthy tissues. Monte Carlo simulations have emerged as indispensable tools for achieving this precision, offering detailed insights into radiation transport and interaction at the subatomic level. As the use of scintillation and luminescence dosimetry becomes increasingly prevalent in radiation therapy, there arises a need for validated Monte Carlo tools tailored to optical photon transport applications. In this paper, an evaluation process of the TOPAS (TOol for PArticle Simulation) Monte Carlo tool for Cerenkov light generation, optical photon transport and radioluminescence based dosimetry is presented. Three distinct sources of validation data are utilized: one from a published set of experimental results and two others from simulations performed with the Geant4 code. The methodology employed for evaluation includes the selection of benchmark experiments, making use of opt3 and opt4 Geant4 physics models and simulation setup, with observed slight discrepancies within the calculation uncertainties. Additionally, the complexities and challenges associated with modeling optical photons generation through luminescence or Cerenkov radiation and their transport are discussed. The results of our evaluation suggests that TOPAS can be used to reliably predict Cerenkov generation, luminescence phenomenon and the behavior of optical photons in common dosimetry scenarios.

Investigation of physical properties of Ba2NdX(X=Nb, Ta)O6 double perovskites for renewable energy applications

Alkali metals at the A site, coupled with rare earth transition metals featuring partly filled 4f and d orbitals at B and B’ sites in A2BB’O6 structure of double perovskites, induce complex d-f electron interactions. Present study explores the rare earth-based double perovskites Ba2NdNbO6 and Ba2NdTaO6, investigating their structural, optoelectronic, magnetic, and thermoelectric characteristics using first principles method. Computational analyses confirm the stable cubic symmetry and ferromagnetic ground state of both compounds. Negative formation enthalpies underline their thermodynamic stability. Spin polarized electronic band structures reveal direct–indirect degeneracy near the Fermi level, dominated by Nd-4f electrons. Optical investigations indicate absorption onset edges at 4.0 eV and significant absorbance peaks in the 6–10 eV range. Furthermore, the investigation into thermoelectric figure of merit reveals capability of Ba2NdNbO6 and Ba2NdTaO6 to efficiently convert heat energy in thermoelectric devices. These findings provide information for potential applications of investigated compounds in thermoelectric (TE) and optoelectronic devices; e.g., in optical absorbers, TE coolers and generators, and photonic devices.

Generation of multi-photon Fock states at telecommunication wavelength using picosecond pulsed light

Multi-photon Fock states have diverse applications such as optical quantum information processing. For the implementation of quantum information processing, Fock states should be generated within the telecommunication wavelength band, particularly in the C-band (1530-1565 nm). This is because mature optical communication technologies can be leveraged for transmission, manipulation, and detection. Additionally, to achieve high-speed quantum information processing, Fock states should be generated in optical pulses with as short a duration as possible, as this allows embedding lots of information in the time domain. In this paper, we successfully generate picosecond pulsed multi-photon Fock states (single-photon and two-photon states) in the C-band with Wigner negativities for the first time, which are verified by pulsed homodyne tomography. In our experimental setup, we utilize a single-pixel superconducting nanostrip photon-number-resolving detector (SNSPD), which is expected to facilitate the high-rate generation of various quantum states. This capability stems from the high temporal resolution of SNSPDs (several tens of picoseconds in our case and also in general) allowing us to increase the repetition frequency of pulsed light from the conventional MHz range to the GHz range, although in this experiment the repetition frequency is limited to 10 MHz due to the bandwidth of the homodyne detector. Consequently, our experimental setup is anticipated to serve as a prototype of a high-speed optical quantum state generator for ultrafast quantum information processing at telecommunication wavelength.

Experimental Observation of Raman Assisted and Kerr Optical Frequency Comb in a 4H-Silicon-Carbide on Insulator Microresonator

Kerr nonlinear microcavities have garnered significant interest owing to their rich dynamics of nonlinear optical phenomena and compatibility with on-chip photonic integration. Recently, silicon carbide has emerged as a compelling platform due to its unique optical properties. In this study, we demonstrate Raman-assisted and Kerr optical frequency generation in a 4H-silicon carbide-on-insulator microresonator. By pumping the transverse electric (TE00) mode within the device, we observe a stimulated Raman scattering (SRS) Stokes with the Raman shift at approximately 775 cm-1, achieved with an on-chip power of 350 mW. Furthermore, by red-tuning the TE00 pump wavelength, we have achieved the coexistence of Raman and Kerr frequency combs. Using another device on the same chip with light variation of the taper we can observe the Raman and Kerr frequency combs within a spectral bandwidth ranging from ∼ 1440 to 1960 nm. The inclusion of the Raman-assisted comb extends the comb’s coverage into longer wavelength regimes, making it highly desirable for spectroscopy applications.

Simultaneous optical and RF linear frequency sweep generation using a Fourier domain mode-locked OEO with carrier-suppressed single sideband modulation

Simultaneous optical and RF linear frequency sweep generation using a Fourier domain mode-locked OEO with carrier-suppressed single sideband modulation

Optic generation and perpetuation of acoustic bubble clusters

Laser-induced cavitation bubbles offer precise control of the flow in space and time, but they are rarely used for the mechanical and chemical processing of liquids. Instead, strong acoustic fields are commonly used to nucleate and drive cavitation bubbles for liquid process applications. While acoustic field creates many more cavitation events, the resulting chaotic dynamics offers little control on the fluid mechanics, i.e., where and how bubbles deliver their energy. Here we present a method that utilizes a laser to nucleate a single cavitation bubble, which is then driven into violent oscillations by the ultrasound field, resulting in splitting of the bubble followed by formation of a cluster of cavitation bubbles. This combination offers means for cavitation control not available in conventional acoustic cavitation. Here, the cavitation bubble is generated with a custom build pulsed laser that is focused below a sonotrode driven at 20 kHz. In absence of the acoustic driving the bubble reaches a maximum diameter of 130 µm with a lifetime of approximately 10 µs. In the presence of the acoustic field the first few expansions and bubble collapses are strongly affected by the phase of nucleation. Over successive acoustic cycles a small bubble cluster develops that loses its connection with the phase of generation. We study the dynamics in the free field and constrained by a rigid boundary. For both geometries the cluster over many acoustic cycles dies off, yet through repetitive optical bubble seeding the cluster lifetime and its location can be controlled.

Direct-modulation optoelectronic oscillator for optical pulse and frequency comb generation

We report the generation of an optical pulse train with a 10 GHz repetition rate in a dual loop direct-modulation optoelectronic oscillator (OEO). Pulse generation is achieved using nonlinear compression in the OEO 5-km-long optical delay line. 3 ps pulses with a timing jitter of 13 fs are reported, while the OEO maintains a phase noise of −133dBc/Hz at 10 kHz from the carrier. Two architectures are compared experimentally and theoretically. A frequency comb with a 1.2 THz linewidth at −30dB is generated.

Sodium yttrium fluoride doped with Er3+ ions for thermally and non-thermally coupled nano-thermometry and IR detection applications

Microwave-assisted combustion synthesis approach was adopted to prepare sodium yttrium fluoride doped with erbium (NaYF4: Er3+) nanoparticles. Powder x-ray diffraction study confirmed the formation of mixed phase of NaY1-xF4: xEr3+ (x = 1, 3, 5, 7 and 9 mol%) sample with cubic and hexagonal phases (predominant). Three characteristic emission peaks appearing at 526, 546 and 670 nm were attributed to the transitions 2H11/2, 4S3/2 and 4F9/2 to 4I15/2 respectively which are characteristic emissions of Er3+ ions when excited with 980 nm radiation. The optimal dopant concentration was determined as 7 mol% of Er3+ ions in yellowish-green region, and the asymmetric ratio was also calculated. The synthesized up-converting sample follows two-photon process for excitation which was confirmed by power law by varying pump-power in the range of 49–143 mW. The thermally and non-thermally coupled levels attributed to the transitions (2H11/2 and 4S3/2), (2H11/2 and 4F9/2) of Er3+ ions were employed to study the temperature sensing which was recorded in 300–550 K and the relative sensitivities were evaluated to be 0.92 and 0.58 %K−1 correspondingly. The significant thermal sensitivity of the synthesized phosphor materials promises its possibility in optical thermometry applications. The synthesized sample when excited with 980 nm laser radiation produced emission in the visible region which facilitates the utilization of sample as infrared (IR) detector. In the purview of solid-state lighting, the luminous efficiency and luminous efficacy of radiation were evaluated as 23.57 % and 161 lm/Wop respectively. The optical thermometry, IR detection and light generation capabilities of the hexagonal-phased sodium yttrium fluoride doped with erbium (NYF:Er) ions are demonstrated with the obtained results.