Design of a Lens System Reduces Chromatic Aberration for Proton Radiography
Jia Qinggang, Wang Wenyuan, Xu Haibo, and Lu Liang
Multi-GeV proton radiography is an important tool for diagnosing density distribution of thick objects. The magnetic lens system called Zumbro lens is widely employed because it compensates for the image distortion induced by small angle multiple Coulomb scattering (MCS) that occurs when the charged protons passing through the object. However, radiography is still suffering from chromatic aberration induced blurring, if the momentum of transmitted proton is different from the reference value of Zumbro lens. In this paper, two methods are employed to reduce chromatic aberration. The first is based on magnetic lens optimization. In addition, a new lens system is first proposed locating the downstream of Zumbro. It is named “auxiliary” lens, which can correct the chromatic aberration for certain protons with momentum far away from the reference of Zumbro lens. Monte Carlo simulation shows that this proposed lens can decrease chromatic aberration and improve the radiography image evidently.
  • Jun. 24, 2022
  • Laser and Particle Beams
  • Vol. 2022 Issue 2 4353314 (2022)
  • DOI:10.1155/2022/4353314
L-Shell X-Ray Conversion Yields for Laser-Irradiated Tin and Silver Foils
Singh R.L., White S., Charlwood M., Keenan F.P., Hyland C., Bailie D., Audet T., Sarri G., Rose S. J., Morton J., Baird C., Spindloe C., and Riley D.
We have employed the VULCAN laser facility to generate a laser plasma X-ray source for use in photoionization experiments. A nanosecond laser pulse with an intensity of order 1015 Wcm-2 was used to irradiate thin Ag or Sn foil targets coated onto a parylene substrate, and the L-shell emission in the 3.3–4.4 keV range was recorded for both the laser-irradiated and nonirradiated sides. Both the experimental and simulation results show higher laser to X-ray conversion yields for Ag compared with Sn, with our simulations indicating yields approximately a factor of two higher than those found in the experiments. Although detailed angular data were not available experimentally, the simulations indicate that the emission is quite isotropic on the laser-irradiated side but shows close to a cosine variation on the nonirradiated side of the target as seen experimentally in the previous work.
  • Jun. 24, 2022
  • Laser and Particle Beams
  • Vol. 2022 Issue 2 3234804 (2022)
  • DOI:10.1155/2022/3234804
Observation of flat-band and band transition in the synthetic space | Article Video
Guangzhen Li, Luojia Wang, Rui Ye, Shijie Liu, Yuanlin Zheng, Luqi Yuan, and Xianfeng Chen
Constructions of synthetic lattices in modulated ring resonators attract growing attention to interesting physics beyond the geometric dimensionality, where complicated connectivities between resonant frequency modes are explored in many theoretical proposals. We implement experimental demonstration of generating a stub lattice along the frequency axis of light, in two coupled ring resonators of different lengths, with the longer one dynamically modulated. Such a synthetic photonic structure intrinsically exhibits the physics of flat band. We show that the time-resolved band structure read-out from the drop-port output of the excited ring is the intensity projection of the band structure onto a specific resonant mode in the synthetic momentum space, where gapped flat band, mode localization effect, and flat-to-nonflat band transition are observed in experiments and verified by simulations. This work provides evidence for constructing a synthetic stub lattice using two different rings, which, hence, makes a solid step toward experimentally constructing complicated lattices in multiple rings associated with synthetic frequency dimensions.
  • Jun. 23, 2022
  • Advanced Photonics
  • Vol. 4 Issue 3 036002 (2022)
  • DOI:10.1117/1.AP.4.3.036002
Loss-tolerant measurement device independent quantum key distribution with reference frame misalignment
Jipeng Wang, Zhenhua Li, Zhongqi Sun, Tianqi Dou, Wenxiu Qu, Fen Zhou, Yanxin Han, Yuqing Huang, and Haiqiang Ma
Reference frame independent and measurement device independent quantum key distribution (RFI-MDI-QKD) has the advantages of being immune to detector side loopholes and misalignment of the reference frame. However, several former related research works are based on the unrealistic assumption of perfect source preparation. In this paper, we merge a loss-tolerant method into RFI-MDI-QKD to consider source flaws into key rate estimation and compare it with quantum coin method. Based on a reliable experimental scheme, the joint influence of both source flaws and reference frame misalignment is discussed with consideration of the finite-key effect. The results show that the loss-tolerant RFI-MDI-QKD protocol can reach longer key rate performance while considering the existence of source flaws in a real-world implementation.
  • Jun. 22, 2022
  • Chinese Optics Letters
  • Vol. 20 Issue 9 092701 (2022)
  • DOI:10.3788/COL202220.092701
Colloidal quantum-dot light emitting diodes with bias-tunable color
Ge Mu, Tianyu Rao, Menglu Chen, Yimei Tan, Qun Hao, and Xin Tang
Although the performance of quantum-dot-based light emitting diodes (QLEDs) has been significantly enhanced over the past years, conventional full-color QLED displays still rely on the side-by-side pattern techniques of red (R)/green (G)/blue (B) quantum dots (QDs). Such lateral integration of multi-color pixels imposes technological difficulty in the development of high-resolution displays due to limited pixel density and fill factors. Herein, we demonstrate the development of full-color QLEDs with bias-tunable emission spectra by engineering mixed R/G/B QDs as light emitting layers. In Commission Internationale de l’Eclairage (CIE) chromaticity coordinates, QLEDs with bias-tunable color exhibit wide color variation ranging from red (0.649, 0.330) to green (0.283, 0.305) to blue (0.255, 0.264) upon increasing voltages and can be tuned to emit white light (0.316, 0.325). More importantly, the fabricated multi-color QLEDs show high luminance approaching 103 cd m-2 and superior external quantum efficiency of 13.3%. Benefitting from the wide spectral tunability and light emitting efficiency, we believe the proposed multi-color QLEDs have great application prospects for both displays and lighting.
  • Jun. 20, 2022
  • Photonics Research
  • Vol. 10 Issue 7 07001633 (2022)
  • DOI:10.1364/PRJ.456043
Synthetic aperture ptychography: coded sensor translation for joint spatial-Fourier bandwidth expansion
Pengming Song, Shaowei Jiang, Tianbo Wang, Chengfei Guo, Ruihai Wang, Terrance Zhang, and Guoan Zheng
Conventional ptychography translates an object through a localized probe beam to widen the field of view in real space. Fourier ptychography translates the object spectrum through a pupil aperture to expand the Fourier bandwidth in reciprocal space. Here we report an imaging modality, termed synthetic aperture ptychography (SAP), to get the best of both techniques. In SAP, we illuminate a stationary object using an extended plane wave and translate a coded image sensor at the far field for data acquisition. The coded layer attached on the sensor modulates the object exit waves and serves as an effective ptychographic probe for phase retrieval. The sensor translation process in SAP synthesizes a large complex-valued wavefront at the intermediate aperture plane. By propagating this wavefront back to the object plane, we can widen the field of view in real space and expand the Fourier bandwidth in reciprocal space simultaneously. We validate the SAP approach with transmission targets and reflection silicon microchips. A 20-mm aperture was synthesized using a 5-mm sensor, achieving a fourfold gain in resolution and 16-fold gain in field of view for object recovery. In addition, the thin sample requirement in ptychography is no longer required in SAP. One can digitally propagate the recovered exit wave to any axial position for post-acquisition refocusing. The SAP scheme offers a solution for far-field sub-diffraction imaging without using lenses. It can be adopted in coherent diffraction imaging setups with radiation sources from visible light, extreme ultraviolet, and X-ray, to electron.
  • Jun. 20, 2022
  • Photonics Research
  • Vol. 10 Issue 7 07001624 (2022)
  • DOI:10.1364/PRJ.460549
Creation of cylindrical vector beams through highly anisotropic scattering media with a single scalar transmission matrix calibration
Qian Zhao, Shijie Tu, Qiannan Lei, Chengshan Guo, Qiwen Zhan, and Yangjian Cai
Cylindrical vector (CV) beams have attracted increasing interest due to their particular properties and their applications in optical imaging, optical manipulation, and light–matter interactions. However, it is challenging to construct CV beams through highly anisotropic scattering media (HASM), such as thick biological tissue, posing a barrier to the applications of CV beams that involve HASM. Here, we present a scheme to construct CV beams beyond high scattering that only requires a single scalar transmission matrix (TM) calibration and manipulation of the spatial degrees of freedom of the scalar input field. Assisted by a radial polarization converter (S-waveplate) and a polarizer, the scheme enables one to obtain the correct incident wavefront for the creation of CV beams through HASM with only one single scalar TM calibration. Compared to the existing method, this user-friendly approach is fast and simple in terms of the optical implements and computations. Both radially and azimuthally polarized beams are experimentally constructed through a ZnO scattering layer to demonstrate the viability of the method. Arbitrarily generalized CV beams and arrays of CV beams are also created through the HASM to further prove the flexibility of the method. We believe this work may pave the way for applications of CV beams that involve a highly anisotropic scattering environment.
  • Jun. 20, 2022
  • Photonics Research
  • Vol. 10 Issue 7 07001617 (2022)
  • DOI:10.1364/PRJ.457928
Object Detection in Optical Remote Sensing Images Based on FFC-SSD Model
Xue Junda, Zhu Jiajia, Zhang Jing, Li Xiaohui, Dou Shuai, Mi Lin, Li Ziyang, Yuan Xinfang, and Li Chuanrong
For the applications of efficient high-precision object detection in optical remote sensing (RS) images, this paper focuses on the difficulty of improving the detection accuracy of the SSD (single shot multibox detector) model on small and densely distributed objects in such images. An improved model FFC-SSD (multi-scale feature fusion & clustering SSD) is thereby proposed. For this purpose, a bounding-box group clustering (BGC) module is designed. Group clustering is implemented to obtain default object frame parameters that are more consistent with the size distribution of object samples and gives more attention to small objects. This module effectively improves the network’s ability to extract object locations. Then, an efficient de-pooling multi-scale feature fusion (MSFF) module is designed to enhance the ability of the model to extract object features and effectively reduce the efficiency loss of the model at the same time. The experimental results demonstrate the effectiveness and applicability of the FFC-SSD model for object detection in optical remote sensing images. The proposed model achieves a favorable balance between precision and efficiency and has high detection accuracy on small objects.
  • Jun. 20, 2022
  • Acta Optica Sinica
  • Vol. 42 Issue 12 1210002 (2022)
  • DOI:10.3788/AOS202242.1210002
Automatic Calibration of Optical Beamforming Network Chip Based on Cascaded Anti-Resonant Microring
Sun Hanwei, Lu Liangjun, Jin Minhui, Liu Jiao, Zhou Linjie, and Chen Jianping
ObjectiveMicrowave phased array antennas (PAAs) have attracted considerable interest owing to their advantages of rapid and accurate beam steering. Traditional PAAs based on electronic phase shifters suffer from the disadvantages of steering angle and instantaneous bandwidth of the radio-frequency (RF) signal due to the beam squinting problem. Integrated optical beamforming networks (OBFNs) use optical true time delay lines (OTTDLs) to broaden the instantaneous bandwidth. The processing RF signal in the optical domain also brings the advantages of low loss, compact size, light weight, and zero electromagnetic interference. Therefore, they can play an important role in broadband large-scale PAA systems. Moreover, the OBFNs can be integrated with other microwave photonic systems, such as optoelectronic oscillators, photonic analog-to-digital converters, and optical channelizing filters to realize fully integrated microwave photonic radars. The most important components in the integrated OBFNs are the OTTDLs. Integrated OTTDLs with a broad bandwidth and large delay tuning range are in high demand. Among the various integrated OTTDL structures, cascaded tunable microring resonators (MRRs) are promising owing to their continuous and broadband delay tuning. Previously, we demonstrated a cascaded-MRRs-based OTTDL chip working at the anti-resonant wavelength. It exhibited the advantages of broadband response with low delay fluctuation, high scalability, and simple control schemes. In this work, we proposed a 1×N binary tree OBFN chip based on cascaded MRRs (Fig. 1). The binary tree topology interlaces the power splitters with the OTTDLs, which effectively reduces the number of delay elements. Due to the random phase errors of MRRs and the thermal crosstalk upon tuning, we proposed and demonstrated an automatic calibration method to facilitate the state calibration of OTTDLs.MethodsFirst, we theoretically investigated the working principle of the OBFN using the transfer matrix method. From the simulated delay spectra, we determined that the anti-resonant MRRs have lower delay fluctuation over a broad bandwidth compared with the on-resonant MRRs (Fig. 2). Moreover, the bandwidth of the OBFN is dependent only on the bandwidth of the continuously tuned MRRs. Therefore, we presented a delay tuning method to increase the system bandwidth by reducing the number of continuously tuned MRRs (Fig. 3). In each stage of the binary tree OBFN, only one MRR was continuously tuned for the delay residual, and the other MRRs were digitally tuned to two specific states (coupling coefficient K=0 or K=1).To correct the random initial states of the MRRs, we developed a control system to automatically perform delay state calibration and characterization (Fig. 5). The calibration procedure includes the following two parts: the optical calibration stage and microwave delay calibration stage (Fig. 6). In the optical calibration stage, we first measured the power efficiency of the MRR phase shifters. Next, the MRRs were calibrated to K=0 and K=1 using the resonance extinction ratio method and the spectrum mean square error method, respectively (Fig. 7). Thereafter, the continuously tuned MRRs were calibrated by aligning the anti-resonant wavelengths to the operating wavelength at various coupling coefficients. The linear power relationship of the MRR tunable coupler and the ring phase shifter was extracted. Considering the inter- and intra-MRR thermal crosstalk, the power relationship could be remedied using a point-slope method (Fig. 8). In the microwave delay calibration stage, the group delay responses of continuously and digitally tuned MRRs were measured. By iterative control of the phase shifters based on the measured delay spectra, we effectively eliminated the influence of thermal crosstalk between the MRRs and obtained a flat delay response in the operating bandwidth.Results and DiscussionsWe experimentally verified the proposed algorithms by testing the longest path of a silicon nitride 1×8 OBFN chip. The chip was fabricated on the TriPLex? platform. The measured delay spectra of a continuously tuned MRR verify the accuracy of the optical calibration (Fig. 9). Due to the thermal crosstalk, the microwave delay calibration procedure is needed for multiple MRRs. Using the proposed method, all the 21 MRRs in the path are digitally tuned and the measured maximum delay is 560 ps with a delay fluctuation of less than 11.2 ps. Moreover, we successfully realize continuous delay tuning of three MRRs. The delay variation is less than 7.5 ps in the bandwidth of 08 GHz (Fig. 10). Comparing our work with other MRR-based OBFN and OTTDL chips, our OBFN controls the largest number of cascaded MRRs for a widely tunable delay range (Table 1). In addition, with the automatic calibration system based on the optical and microwave joint optimization, our proposed OBFN allows for a broad operating bandwidth and a low delay fluctuation.ConclusionsWe proposed a 1×N binary tree OBFN based on tunable cascaded MRRs working at the anti-resonant wavelength. The delay tuning method that utilizes one continuously tuned MRR in one stage expands the operating bandwidth of the OBFN. An automatic calibration system was experimentally verified by testing the longest path of a 1×8 OBFN chip. With the joint optimization algorithm, we realized the accurate calibration of 21 MRRs automatically. This method, with reduced system complexity, can be further used to calibrate the entire OBFN chip.
  • Jun. 20, 2022
  • Chinese Journal of Lasers
  • Vol. 49 Issue 11 1119001 (2022)
  • DOI:10.3788/CJL202249.1119001
10 PW peak power femtosecond laser pulses at ELI-NP
Christophe Radier, Olivier Chalus, Mathilde Charbonneau, Shanjuhan Thambirajah, Guillaume Deschamps, Stephane David, Julien Barbe, Eric Etter, Guillaume Matras, Sandrine Ricaud, Vincent Leroux, Caroline Richard, François Lureau, Andrei Baleanu, Romeo Banici, Andrei Gradinariu, Constantin Caldararu, Cristian Capiteanu, Andrei Naziru, Bogdan Diaconescu, Vicentiu Iancu, Razvan Dabu, Daniel Ursescu, Ioan Dancus, Calin Alexandru Ur, Kazuo A. Tanaka, and Nicolae Victor Zamfir
  • Jun. 17, 2022
  • High Power Laser Science and Engineering
  • Vol. 10 Issue 3 03000e21 (2022)
  • DOI:10.1017/hpl.2022.11
Optics Physics Geography All Subjects

Special lssue

Special Issue on Relativistic Laser Plasma Interaction (RLPI) Diagnostics and Instrumentation (2022)

Submission Open:1 June 2022; Submission Deadline: 31 December 2022

Editor (s): Joerg Schreiber, Rodrigo Lopez-Martens, Lieselotte Obst-Huebl, Jianhui Bin

Future Control Systems and Machine Learning at High Power Laser Facilities (2022)

Submission Open:1 March 2022; Submission Deadline: 31 August 2022

Editor (s): Andreas Döpp, Matthew Streeter, Scott Feister, Hyung Taek Kim, Charlotte Palmer