Early Posting

Accepted papers to appear in an upcoming issue

Optica Publishing Group posts prepublication articles as soon as they are accepted and cleared for production. See the FAQ for additional information.

Tunable O-band high-tolerance silicon mode multiplexer based on phase-mismatched asymmetric directional couplers

Kodai Nakamura, Takeshi Fujisawa, Takanori Sato, and Kunimasa Saitoh

DOI: 10.1364/JOSAB.515894 Received 12 Dec 2023; Accepted 18 Mar 2024; Posted 18 Mar 2024  View: PDF

Abstract: Small silicon-on-insulator (SOI)-based tunable O-band TE0-TE1 and TE0-TE2 mode multiplexers (MUXs) based on phase-mismatched asymmetric directional couplers (ADCs) and phase-adjustment region are theoretically and experimentally demonstrated. We designed ADCs with an intentionally phase-mismatched coupling region to suppress wavelength dependence and improve fabrication error tolerance. Even at worst, the fabricated O-band TE0-TE2 mode MUX has −0.71 dB transmission. Moreover, to improve performance, we proposed and designed three-section tapered ADCs (3STADCs) divided into three regions. We theoretically show that the TE0-TE1 and TE0-TE2 mode MUXs based on the 3STADC have more than −0.28 dB and −0.36 dB transmission, respectively.

High efficiency independent modulation at dual-wavelength based on Pancharatnam-Berry and propagation phases

Minglei He, Jiepeng Wu, Haohan Chen, Hao Wang, Xinen Wu, Qianbin Feng, Qiwen Wu, Xiaosong Wu, Haiying Liu, Qiang Li, and Lijun Wu

DOI: 10.1364/JOSAB.516201 Received 21 Dec 2023; Accepted 18 Mar 2024; Posted 18 Mar 2024  View: PDF

Abstract: Metasurfaces capable of controlling multiple wavelengths independently have attracted broad interests these years due to their significance in multi-channel information processing applications. Previous solving strategies include spatial multiplexing or extensive searching for appropriate structures, both of which have their own disadvantageous, such as low efficiency, large computer resource requirement or time-consuming. In this paper, by combining the Pancharatnam-Berry (PB) phase and propagation phase, we propose a strategy to simplify the design complexity in a dual-wavelength metasurface system, in which two simplest rectangular-shaped dielectric pillars (T₁ and T₂) with different aspect ratios are chosen as basic structures and crossed at the geometric center to achieve manipulation. The larger pillar T₂ controls the longer wavelength through the PB phase while the smaller T₁ acts a perturbation to T₂. The crossed T₁&T₂ is studied as a whole to tune the short wavelength. The investigations by the multipole expansion method reveals that the polarization conversion ratio of the meta-atoms is dependent on the interference of the formed multipoles. To validate the proposed strategy, a dual-wavelength achromatic metalens and a wavelength-multiplexed holographic metasurface operating at the infrared thermal imaging band are designed. Our design strategy can find widespread applications in metasurfaces where multiple objectives are required to realize.

Low-kappa DBR grating filters on an InP Generic Photonic Integration Foundry Platform

Rakesh Ranjan Kumar, Andreas Hänsel, Pau Castera, Nicolas Volet, and Martijn Heck

DOI: 10.1364/JOSAB.518800 Received 16 Jan 2024; Accepted 18 Mar 2024; Posted 18 Mar 2024  View: PDF

Abstract: We demonstrate narrow-bandwidth, low-kappa, DBR grating filters on an Indium phosphide generic foundry platform. With the varying corrugation widths of the DBR grating, we achieve flexibility in the design of the coupling coefficients from 10 to 50 cm-1, which correspond to grating bandwidths of 0.67 nm to 1.28 nm, respectively. These values are experimentally observed and agree well with the theoretical analysis. The DBR grating is based on periodic rectangular grooves in quaternary material that is placed between the waveguide core and cladding region. Such configurations of DBR grating provide a low propagation loss of ~2 dB/cm near the telecom band around 1550 nm.

Super-resolution spectroscopy via spectrum slicing with a Fabry-Pérot cavity

Lin Chen, peng yang, Boya Xie, and Sheng Feng

DOI: 10.1364/JOSAB.516769 Received 21 Dec 2023; Accepted 15 Mar 2024; Posted 15 Mar 2024  View: PDF

Abstract: Spectroscopy is one of the most powerful technical tools that are widely used in the study of natural sciences and the development of high technologies. To improve the performance of a traditional dispersive spectrometer, there is a competition between its spectral resolution and the geometric volume; a higher resolution is usually accompanied by a higher cost as well. However, a growning body of evidence suggests an urgent demand for miniaturized spectrometers with high spectral resolution and low costs. In this paper, we propose and study super-resolution spectroscopy via spectrum slicing by use of a Fabry–Perot (FP) cavity combined with a traditional spectrometer. The cavity functions as a spectral filter to slice into discrete pieces the continuous spectrum of the input light. For each given cavity length, the cavity outputs a set of sliced spectral pieces that are then analyzed and recorded by the subsequent spectrometer. By scanning the cavity length, one will have multiple sets of sliced spectral pieces that are then finally fused to recover a resolution-enhanced copy of the input spectrum. A theoretical analysis for the super-resolution spectroscopy is provided to prove the feasibility of the proposal, as further confirmed by Matlab numerical simulation. The studied spectral analysis technique will benefit the research fields in need of high resolution spectrometers with moderate device volumes and low costs.

Laser-pump-resistive-probe technique to study nanosecond-scale relaxation processes

Mark Blumenau and Alexander Kuntsevich

DOI: 10.1364/JOSAB.517905 Received 08 Jan 2024; Accepted 14 Mar 2024; Posted 15 Mar 2024  View: PDF

Abstract: Standard optical pump-probe methods analyze a system's temporal response to a laser pulse within sub-femtoseconds to several nanoseconds, constrained by the optical delay line's length. While resistance is a sensitive detector in various fields, its measurements are typically slow (>microseconds) due to stabilization requirements. We suggest here atime-resolved pump-probe technique which combines an optical "Pump" pulse and a rectangular electrical "Probe" pulse through the sample, measuring transmission in a 50 Ohm matched circuit with a digital oscilloscope. This allows electrically-driven delays from nanoseconds to seconds. Demonstrations include studying heat-induced changes in a thin amorphous VO$_x$ film and carrier relaxation in a CdS photoresistor, showcasing potential applications in heat transfer, biochemical reactions, and gradual electronic transformations.

Nickel composite film for terahertz wave broadband absorption

Quanjun Liu, Fangrong HU, An Su, Mingzhu Jiang, Zhang Longhui, and Zihang Song

DOI: 10.1364/JOSAB.518599 Received 16 Jan 2024; Accepted 14 Mar 2024; Posted 15 Mar 2024  View: PDF

Abstract: Due to the poor response of natural materials in the terahertz (THz) frequency band, ultra-broadband absorption of THz wave is a challenge. In this work, a nickel-composite-film (NCF) is experimentally demonstrated for the ultra-broadband absorption of THz wave. The NCF consists of nickel foam, polydimethylsiloxane (PDMS) and few-layer of graphene. The nickel foam has three-dimensional structure which can be filled by the PDMS and few-layer of graphene. By controlling the mass fraction of few-layer graphene in the PDMS, we can reduce the surface reflection of THz wave and achieve broadband absorption. For a 0.5-mm-thick of NCF, when the mass fraction of doped few-layer graphene is 2%, the qualified bandwidth (with absorption rate more than 90%) reaches 3.2 THz. More importantly, for different thicknesses of nickel foams, the absorption bandwidth can be enhanced by changing the mass fraction of few-layer graphene.

Tunable Non-Specular Effects on Hyperbolic Crystal Coated with Single Layer of Graphene

Waleed waseer, QAisar Naqvi, and Maria Iqbal

DOI: 10.1364/JOSAB.516149 Received 27 Dec 2023; Accepted 13 Mar 2024; Posted 14 Mar 2024  View: PDF

Abstract: In this work, we have theoretically investigated the tunable non-specular effects, specifically Imbert-Fedorov andGoos-H¨anchen shifts on a graphene-based uniaxial hyperbolic crystal geometry. The hyperbolic crystal is made ofhexagonal boron nitride and the source of excitation is a circularly polarized light beam. The influence of chemicalpotential and absolute temperature of the graphene on these effects is examined. Notably, the research reveals that, theshifts exhibit complex and significantly varying behavior within and outside the infrared reststrahlen frequency-bandsof hyperbolic crystal.

Fano resonance and enhanced sensing in the excitation of surface phonon polariton

Qiwen Zhao, Chenyi Yao, Ying He, yanfang yang, and Hui-Fang Zhang

DOI: 10.1364/JOSAB.518702 Received 16 Jan 2024; Accepted 13 Mar 2024; Posted 14 Mar 2024  View: PDF

Abstract: The surface phonon polariton is a collective oscillation mode of phonons and incident electromagnetic waves in polar dielectric materials. Compared with surface plasmon polaritons, it has low loss and can be applied to the mid-infrared band. A Surface phonon resonance sensor based on waveguide-coupling is proposed. The sensor structure is a typical Kretschmann configuration consisting of a germanium (Ge) prism, a silicon carbide (SiC) layer, diindium triselenide (In2Se3) , Titanium Dioxide (TiO2), and the surrounding dielectrics. The reflectivity possesses significant asymmetric Fano-resonance dips. The sensitivity and Q-factor of the proposed sensor can be enhanced by and . Our investigation provides an alternative method for refractive index sensing, thus opening up opportunities for the design of various phonon devices based on Fano-resonance.

In-situ holograms and two-wave mixing amplification of conical diffraction vector waves

Muhammad Waqar Iqbal, Yuliia Shiposh, Anton Kohutych, Nicolas Marsal, Alexander Grabar, and Germano Montemezzani

DOI: 10.1364/JOSAB.517056 Received 27 Dec 2023; Accepted 12 Mar 2024; Posted 13 Mar 2024  View: PDF

Abstract: Holographic recording and selective reconstruction and amplification of conical diffraction vector waves is demonstrated using a nonlinear photorefractive Sn₂P₂S₆ crystal acting simultaneously as medium producing the conical diffraction effect and as holographic storage material. It is shown that upon propagation of the object wave along one of the optical axes of the biaxial crystal, the azimuthal spreading of the local linear polarizations across the conical diffraction ring allows its holographic recording with any combinations of the object and reference wave's input polarizations, including mutually orthogonal ones. We discuss the dependence of the recording and read-out polarizations on the recovered and amplified patterns and provide a simplified model qualitatively accounting for all the main observed features. The approach permits a tailoring of the reconstructed or amplified vector waves in terms of intensity and polarization distributions and opens interesting perspectives for their static or dynamic manipulation.

Berry phase and the Mandel parameter of the non-degenerate parametric amplifier

Juan Vega, Enrique Choreño, Didier Ojeda-Guillén, and Roberto Mota

DOI: 10.1364/JOSAB.517533 Received 03 Jan 2024; Accepted 10 Mar 2024; Posted 15 Mar 2024  View: PDF

Abstract: We study the non-degenerate parametric amplifier problem from an algebraic approach of the $SU(1,1)$ group. We write the Hamiltonian of this problem in terms of the boson generators of the $SU(1,1)$ group and the difference operator. We apply the tilting transformation to our results to exactly solve this Hamiltonian and obtain its energy spectrum and eigenfunctions. Then, by assuming that our Hamiltonian is an explicit function of time we calculate its Berry phase. Finally we obtain the Mandel $Q-$parameter of the photon numbers $n_a$ and $n_b$.

Multiple electromagnetically induced grating in the 85Rb five-level atomic medium

Anh Nguyen Thi Quynh, Bang Nguyen, Anh Ha Thi Quynh, Anh Truong Chu Van, Mai Ngo Thi Tuyet, Nhung Nguyen Thi, Nhu Trinh Thi, My Le Tra, Huyen Le Thi Minh, Hung Ngo Tien, and Doai Le

DOI: 10.1364/JOSAB.517939 Received 08 Jan 2024; Accepted 07 Mar 2024; Posted 07 Mar 2024  View: PDF

Abstract: In this work, multiple electromagnetically induced grating is realized based on multiple electromagnetically induced transparency in the 85Rb five-level atomic medium. We demonstrate that the diffraction pattern of the probe light field is observed at three different frequency regions corresponding to the three transparent spectral regions of the system. The influence of the intensity and frequency of the coupling laser field on the diffraction pattern of electromagnetically induced grating and its diffraction efficiency is also investigated, which can find the optimal parameters to improve the high-order diffraction efficiency. The appearance of multiple electromagnetically induced grating in multi-level atomic systems can be applied to photonic devices operating with multiple frequency channels.

Multi-tap microwave photonic filter based on DFB laser array using photonic wire bonding

zhenzhen Xu, tongtong yang, Zhenxing Sun, Yipeng Mei, Jun LU, Wenxuan Wang, Yuxin Ma, and Xiangfei Chen

DOI: 10.1364/JOSAB.522616 Received 28 Feb 2024; Accepted 06 Mar 2024; Posted 11 Mar 2024  View: PDF

Abstract: We propose and experimentally demonstrate a multi-tap microwave photonic filter (MPF) based on a distributed feedback (DFB) laser array using photonic wire bonding (PWB). Through the application of the PWB technique, an eight-wavelength DFB laser array with wavelength spacing of 400 GHz was hybrid integrated with an arrayed waveguide grating (AWG) multiplexer. Remarkably, the insertion losses of all eight channels are maintained below 5 dB. In the experiments, the larger wavelength spacing allowed us to achieve a sinc MPF with a lower 3-dB bandwidth of 0.22 GHz using only 8 taps. Furthermore, Gaussian apodization enabled the out-of-band rejection of the filter to reach 24 dB. These results indicate that the proposed scheme could provide a promising guideline for the MPFs that demand both high reconfigurability, and greatly reduced size and complexity

Optical reciprocity-nonreciprocity-amplification conversion based on degenerate four-wave mixing

dan song, xin li, haitao zhou, jingjing xue, ruonan Li, Dan Wang, Baodong Yang, and junxiang zhang

DOI: 10.1364/JOSAB.515734 Received 13 Dec 2023; Accepted 06 Mar 2024; Posted 07 Mar 2024  View: PDF

Abstract: Optical nonreciprocity plays an important role in optical communication and quantum networks. In this research, we propose and demonstrate a conversion scheme of magnetic-free dual-channel optical reciprocal amplification (RA) and nonreciprocal amplification (NRA) based on the multiple degenerate four-wave mixing (FWM) process in hot atoms. In our experiment, the dual-channel NRA works with the action of a single pump field based on the establishment of FWM in the same direction and break in the opposite direction. Based on stable ground-state Zeeman coherence, by introducing a counter-propagating pump field again, NRA can be changed to RA in the opposite direction of the two original amplified conjugate signals. Moreover, the frequencies of RA signals are very dependent on those of co-propagating pump fields. The experimental realization of NRA-RA conversion may have applications for multichannel angular momentum spatial multiplexing and quantum gate manipulation.

Shaping of reflective microjet via adding a metal mask onto dielectric scatterer

Yu-Jing Yang and De-Long Zhang

DOI: 10.1364/JOSAB.516638 Received 20 Dec 2023; Accepted 06 Mar 2024; Posted 07 Mar 2024  View: PDF

Abstract: The method of shaping reflective microjet (MJ) via adding a metal mask onto dielectric scatterer is proposed. The study focuses on the effects of size, shape of metal mask, and shape of scatterer on the performance of MJ. The results show that the mask size is a vital factor in tailoring the characteristic parameters of MJ, especially the focal length (FL). With a properly designed mask size, the FL can increase by 0.51λ, as much as four times of the FL of MJ generated without metal mask. The mask size dependence of MJ parameters is related to the change of number and position of phase singularity in Poynting vector distribution. And the shapes of mask and scatterer only slightly affect the optimal mask size at which the FL maximizes. The proposed method can be used to effectively tailor the FL of reflective MJ to meet the requirement by various applications.

The genuine five-partite quantum steering generated by an injection signal optical parametric oscillation cascaded with two sum-frequency processes

X. Y. Cheng, Y. R. Shen, J. W. Lv, Y. X. Jiang, L. Cheng, Youbin Yu, and Aixi Chen

DOI: 10.1364/JOSAB.511578 Received 07 Nov 2023; Accepted 05 Mar 2024; Posted 05 Mar 2024  View: PDF

Abstract: Multipartite quantum steering is an important quantum resource and the basis of quantum computing and quantum secure communication. In this paper, a scheme is proposed to produce genuine five-partite quantum steering by an injected signal optical parametric oscillation cascaded with two sum-frequency processes. First, idler beam is generated by a difference-frequency generation process between pump and injected signal in an optical superlattice. By using the quasi-phase-matching technique, two sum-frequency beams are generated by the sum-frequency processes of pump and idler beams as well as pump and injected signal in the same optical superlattice. It is found that the genuine five-partite steering exists by applying a criterion for genuine multipartite quantum steering. Finally, the variation properties of the quantum steering with parameters are discussed. The genuine five-partite quantum steering generated by present scheme has potential applications in quantum computing and quantum secure communication.

Ultrafast random polarization beam smoothing driven by rotating wavefront via optical Kerr effect

hao xiong, Zheqiang Zhong, and Bin Zhang

DOI: 10.1364/JOSAB.495471 Received 16 May 2023; Accepted 21 Feb 2024; Posted 22 Feb 2024  View: PDF

Abstract: We propose an ultrafast random polarization smoothing scheme to enhance irradiation uniformity and randomize polarization of the focal spot. In the scheme, each beamlet in a laser quad is driven by a rotating petal-like wavefront, giving rise to the ultrafast redistribution of the speckles within the focal spot and thus improving the irradiation uniformity of the focal spot. The rotating wavefront is induced by an optical Kerr medium pumbed by a laser beam with rotating intensity distribution that is generated by the superposition of two Laguerre-Gaussian beams carrying conjugate vortex phase and frequency shift. In addition, by properly selecting the topological charges of the pump beams and polarization states of the beamlets, the beamlets in a quad can be divided into two sets with counter-rotating wavefronts and orthogonal polarizations, which further randomizes the polarization of the focal spot. The ultrafast random polarization smoothing scheme is expected to improve the beam smoothing and polarization randomizing performance.

Accelerating Finite-Difference Frequency-Domain Simulations for Inverse Design Problems in Nanophotonics using Deep Learning

Lukas Schulte, Marco Butz, Marlon Becker, Benjamin Risse, and Carsten Schuck

DOI: 10.1364/JOSAB.506159 Received 18 Sep 2023; Accepted 15 Feb 2024; Posted 16 Feb 2024  View: PDF

Abstract: Inverse design of nanophotonic devices becomes increasingly relevant for the development of complex photonic integrated circuits. Electromagnetic first-order simulations contribute the overwhelming computational cost to the optimization routines in established inverse design algorithms, requiring more efficient methods for enabling improved and more complex design process flows. Here we present such a method to predict the electromagnetic field distribution for pixel-discrete planar inverse designed structures using deep learning. Our model is able to infer accurate predictions used to initialize a conventional Finite Difference Frequency-Domain-algorithm and thus lowers the time required for simulating the electromagnetic response of nanophotonic device layouts by about 50 %. We demonstrate the applicability of our deep learning method for inverse design of photonic integrated powersplitters and mode convertersand we highlight the possibility of exploiting previous learning results in subsequent design tasks of novel functionalities via finetuning on reduced data sets, thus improving computational speed further.

Generalized Bloch boundary conditions based on symmorphic space group and the finite-element implementation in photonic crystal

Jingwei Wang, Lida Liu, Zhanwen Wang, Yuhao Jing, and Yuntian Chen

DOI: 10.1364/JOSAB.514857 Received 08 Dec 2023; Accepted 14 Feb 2024; Posted 13 Mar 2024  View: PDF

Abstract: We study generalized Bloch boundary conditions and its finite element implementation within the theoretical framework of symmorphic space group. By combining translation symmetry operations with mirror and rotational symmetry operations, we develop a procedure for implementing generalized Bloch boundary conditions in finite element method (FEM) for periodic photonic structures. Firstly, we lay out the theoretical foundation and numerical implementation of generalized Bloch boundary conditions in FEM. We illustrate the proposed method via 2D/3D periodic photonic structures. Without loss of generality, we calculate the band structures of 2D/3D photonic crystals using our proposed generalized Bloch boundary and benchmark the results against the conventional Bloch boundary conditions. The comparisons show that band structure and eigenmode yield excellent agreements with the results obtained from conventional Bloch boundary conditions. However, our method has improved computational efficiency by at least two-fold. We further elaborate the comparisons with computation errors, memory efficiency and computation times, all of which indeed show that our proposed method outperforms the conventional one due to careful considerations of the mirror and rotational symmetry operation, apart from the translation symmetry. In addition, our method can easily be extended to other methods such as FDTD and transfer matrix.

Photonic crystal fiber sensors to excite surface plasmon resonance based on elliptical detection channels are used for highly sensitive magnetic sensing

Hujun Tang, Feifei Sun, Tao Shen, Feng Yue, Chi Liu, Xin Liu, and Chao Wang

DOI: 10.1364/JOSAB.506522 Received 21 Sep 2023; Accepted 03 Feb 2024; Posted 08 Feb 2024  View: PDF

Abstract: To improve the detection performance of fibre optic magnetic field sensors a new photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) was designed and investigated. The designed sensor uses an elliptical detection channel, and the modal transmission characteristics and magnetic field sensing characteristics of this fiber optic sensor are analyzed using the Full Vector Finite Element Method (FVFEM). In addition, the effect of the detection channel on the detection accuracy at different curvatures was investigated. Compared with previous optical fiber magnetic field (MF) sensors, the designed sensor meets the requirements of both refractive index (RI) and MF measurements, and the MF sensitivity, refractive index (RI) sensitivity, and amplitude sensitivity (AS) of the sensor reach 0.739 nm/Oe,12043.8nm/RIU, and 754.88 RIU-1, respectively. The designed sensor expands the application range of optical fiber sensors and reduces the cost. It has great potential for application in complex environments.