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Optics Letters

Qiwei Xu, Lingju Meng, Tao Zeng, Kaustubh Sinha, Carson Dick, Xihua Wang
Solution-processed semiconductors that exhibit tunable light absorption and can be directly integrated into state-of-the-art silicon technologies are attractive for near-infrared (NIR) light detection in applications of medical imaging, night vision cameras, hyperspectral sensing, etc. Colloidal quantum dot (CQD) is regarded as a promising candidate for its solution-processability and superior optoelectronic properties. Here we propose an on-chip CQD photodetector, photodiode-oxide-semiconductor field-effect transistor, for NIR light sensing...
January 15, 2019: Optics Letters
Cailing Fu, Yiping Wang, Zhiyong Bai, Shen Liu, Yan Zhang, Ziliang Li
A novel twist-direction-dependent high-order orbital angular momentum (OAM) generator based on an inflated helical photonic crystal fiber (IHPCF) was demonstrated by use of an inflation-assisted hydrogen-oxygen flame heating technique. Compared with the helical photonic crystal fiber, the IHPCF exhibits a perfect transmission dip without distinct splits, thus generating high-quality OAM±6 modes. The helical phase of the generated OAM modes is dependent on the twist direction of the IHPCF and independent of the polarization state of the input light...
January 15, 2019: Optics Letters
Jianlei Wang, Qingsong Song, Yangwei Sun, Yongguang Zhao, Wei Zhou, Dongzhen Li, Xiaodong Xu, Chongfeng Shen, Weichao Yao, Li Wang, Jun Xu, Deyuan Shen
We report on, to the best of our knowledge, the first Q-switched single-crystal fiber (Ho:YAG SCF) laser in the 2 μm spectral range, in-band pumped by a Tm-doped all-fiber laser. A continuous-wave laser with 12.5 W output power and Q-switched laser with 1.44 mJ pulse energy and 7.5 ns pulse duration at a repetition rate of 1 kHz were demonstrated. The high laser performance is attributed to the high gain, suppressed nonlinear effects, and easy thermal management which benefited from the unique geometric construction of the SCF...
January 15, 2019: Optics Letters
Bingzheng Yan, Baitao Zhang, Jingliang He, Hongkun Nie, Guoru Li, Junting Liu, Bingnan Shi, Ruihua Wang, Kejian Yang
In this Letter, a high-quality saturable absorber (SA) based on a multilayered two-dimensional ternary chalcogenide Ta2 NiS5 with a narrow bandgap, has been successfully fabricated and used as a SA in a 1.9 μm spectral region. The nonlinear saturable absorption properties of the as-prepared SA have been investigated by using an open-aperture Z-scan method. A passively Q-switched all-solid-state laser operating at 1.9 μm has been realized with the Ta2 NiS5 SA. The maximum average output power, shortest pulse width, pulse energy, and pulse peak power from the passively Q-switched (PQS) laser are 1...
January 15, 2019: Optics Letters
Jin-Hun Kim, Yong Sup Ihn, Yoon-Ho Kim, Heedeuk Shin
The development of quantum photonic information technology demands high-quality photon sources. Here we demonstrate a low-noise and high-speed photon source generated by the spontaneous four-wave mixing process in a micro/nanofiber (MNF). The pair generation in a MNF is tailorable by controlling its diameter and designed for creating signal and idler photons in the silicon-based detector wavelength range, yielding high detection efficiency and coincidence count rate. This MNF photon source can be coupled to other fiber systems with negligible coupling loss and can be efficiently exploited as fiber-based quantum light sources for quantum information applications...
January 15, 2019: Optics Letters
Zihan Geng, Deming Kong, Bill Corcoran, Pengyu Guan, Francesco Da Ros, Edson Porto da Silva, Leif Katsuo Oxenløwe, Arthur James Lowery
We propose a novel scheme with a "time-lens"-based partial optical Fourier transform (OFT) and coherent sampling for high-speed complex orthogonal frequency-division multiplexing (OFDM) signal detection. Compared with all-optical OFDM demultiplexing with a matched optical filter, our proposed method replaces specialized optical filters with commercially available equipment, which relaxes stringent manufacturing and operational requirements. Our simulation shows that even with a partial OFT, theoretically, close to inter-channel interference-free performance is possible...
January 15, 2019: Optics Letters
Mustafa Hammood, Ajay Mistry, Minglei Ma, Han Yun, Lukas Chrostowski, Nicolas A F Jaeger
In this work, we present optical add/drop multiplexer (OADM) filters for coarse wavelength-division-multiplexing (CWDM) systems with high sidelobe suppressions that result in high adjacent channel isolations (Ai ). The filters are realized by using a compact, series-cascaded configuration of apodized, contradirectional-coupling-based filters. We experimentally demonstrate a device with a measured Ai of 53 dB (these devices hold the promise of achieving even higher Ai s). While having large Ai s, our devices have the wide bandwidths and low insertion losses required for CWDM applications...
January 15, 2019: Optics Letters
Rui Cheng, Han Yun, Stephen Lin, Ya Han, Lukas Chrostowski
It is shown that an apodization profile to realize a specific spectral response for a silicon integrated Bragg grating (IBG) can be amplified/scaled-up greatly by an order of magnitude by introducing phase delays between the two sides of the apodized gratings. This amplification brings about significant improvements in the apodization dynamic range and resolution/precision, thereby facilitating the spectral tailoring of the IBGs. The concept is first exploited in corrugation width-modulated Gaussian-apodized silicon IBGs, and then in phase-modulated silicon IBGs to achieve a five-channel dispersionless square-shaped filter...
January 15, 2019: Optics Letters
Jing Zhang, Xiaohui Zhao, Yuanlin Zheng, Xianfeng Chen
The generalized nonlinear Snell's law at the χ(2) modulation surface is deduced from the universal model of χ(2) processes in nonlinear photonic crystals (NPhCs). Based on the generalized nonlinear Snell's law, the anomalous refraction and reflection geometries are predicted and observed at crystal's inner boundary on nonlinear metasurfaces formed by one-dimensional NPhCs. The emitted second harmonic is observed, which obeys the law and appears to turn into multiple orders compared to that in a bulk crystal...
January 15, 2019: Optics Letters
Zhongsheng Man, Xiujie Dou, Shenggui Fu
We show that elongating a tightly focused field in the direction perpendicular to the optical axis is possible. We demonstrate our approach by specially shaping the Pancharatnam-Berry (PB) phase. Moreover, the analytical formulae required to calculate the strength vectors and energy flux of the three-dimensional electromagnetic fields near the focus of an aplanatic optical system are derived using the Richards and Wolf vectorial diffraction methods. Calculations reveal that the transverse enhancement is controllable and depend on the phase index in the PB phase, thereby giving rise to a focus with tunable length and subwavelength width in the focal plane...
January 15, 2019: Optics Letters
Gayathri Bharathan, Toney Teddy Fernandez, Martin Ams, Robert I Woodward, Darren D Hudson, Alex Fuerbach
We report the direct femtosecond laser inscription of type-I fiber Bragg gratings (FBGs) into the core of soft-glass ZBLAN fibers. We investigate and compare various fabrication methods such as single pass (line by line), double pass, and stacking (plane by plane) to create the highest reflectivity FBGs (99.98%) for mid-infrared (mid-IR) applications. In addition, we experimentally demonstrate how the parameters that influence the coupling coefficient, i.e., refractive index modulation and overlap factor, can be controlled in these gratings to specifically tailor the FBG properties...
January 15, 2019: Optics Letters
Michael I Mishchenko, Maxim A Yurkin
We use the volume integral equation formulation of frequency-domain electromagnetic scattering to settle the issue of additivity of the extinction, scattering, and absorption cross sections of a fixed tenuous group of particles. We show that all the integral optical cross sections of the group can be obtained by summing up the corresponding individual-particle cross sections, provided that the single-scattering approximation applies.
January 15, 2019: Optics Letters
Borja Jerez, Frederik Walla, Andrés Betancur, Pedro Martín-Mateos, Cristina de Dios, Pablo Acedo
An absolute-frequency terahertz (THz) dual-frequency comb spectrometer based on electro-optic modulators for tunable, high-resolution, and real-time rapid acquisition is presented. An optical line of a master frequency comb (filtered via optical injection locking) serves as the seed to electro-optically generate a pair of new frequency combs (probe and local oscillator). Photomixing both combs with another coherent line from the same original master comb generates a narrow linewidth THz dual-comb with teeth frequencies that can be referenced to a radio-frequency standard...
January 15, 2019: Optics Letters
Seong-Hwan Kim, Jong-Bum You, Yun-Gi Ha, Geumbong Kang, Dae-Seong Lee, Hyeonho Yoon, Dong-Eun Yoo, Dong-Wook Lee, Kyoungsik Yu, Chan-Hyun Youn, Hyo-Hoon Park
We demonstrate longitudinal beam-steering with a 1×16 silicon optical phased array (OPA) using a monochromatic light source and thermo-optic control of the refractive index in the grating radiator region. The refractive index is controlled by forming a series of n-i-n heaters, placing i-regions in each radiator of the OPA. When the biased voltage in the heaters is increased, the refractive index of the radiator region is increased by the thermo-optic effect, and the longitudinal radiation angle is changed according to the Bragg condition...
January 15, 2019: Optics Letters
Joan Manel Ramirez, Qiankun Liu, Vladyslav Vakarin, Xavier Le Roux, Jacopo Frigerio, Andrea Ballabio, Carlos Alonso-Ramos, Enrico Talamas Simola, Laurent Vivien, Giovanni Isella, Delphine Marris-Morini
Long-wave infrared photonics is an exciting research field meant to revolutionize our daily life by means of key advances in several domains including communications, imaging systems, medical care, environmental monitoring, or multispectral chemical sensing, among others. For this purpose, integrated photonics is particularly promising owing to its compactness, mass fabrication, and energy-efficient characteristics. We present in this Letter, for the first time to the best of our knowledge, broadband integrated racetrack ring resonators operating within the crucial molecular fingerprint region...
January 15, 2019: Optics Letters
Weiwei Chen, Hao Lu, Shiqi Li, Pengjun Wang, Shixun Dai, Tianjun Yang, Bohao Zhang, Ruolan Yu, Qiang Fu, Jun Li, Yan Li, Tingge Dai, Yuehai Wang, Jianyi Yang
An integrated flexible-grid 1×2 wavelength-selective switch based on reconfigurable add-drop silicon microring resonators using strip waveguides is designed and experimentally demonstrated. By flexibly tuning the resonance of microring resonators and path phase differences via the thermo-optic effect, the transmission spectra with adjustable bandwidths can be formed as desired at the output ports. Our experimental results reveal that the fabricated flexible-grid 1×2 wavelength-selective switch provides crosstalk lower than -10...
January 15, 2019: Optics Letters
Mao Ye, Vishva Ray, Yueheng Peng, Wei Guo, Ya Sha Yi
A emerging optical metasurface has raised wide interest due to its planar structure and unprecedented control of light through subwavelength nano structures. In this study, we propose a novel metalens that integrates the function of a concentrating lens and linear polarizer. For this lens, focus can only be formed under the incidence of designed linear polarization, and its focusing effect is significantly suppressed upon the incidence of the orthogonal polarization. The linear polarization distinguishing focus characteristic is from the special design of anisotropic subwavelength phase shifters with two functionalities...
January 15, 2019: Optics Letters
Yuchen Wang, Frédéric Jobin, Simon Duval, Vincent Fortin, Paolo Laporta, Martin Bernier, Gianluca Galzerano, Réal Vallée
We report a passively mode-locked Dy3+ :fluoride fiber laser emitting around 3.1 μm based on the nonlinear polarization evolution technique in a ring configuration, using in-band pumping at 2.8 μm. Transform-limited and self-starting mode-locked pulses as short as 828 fs with a center wavelength around 3.1 μm and repetition rates up to 60 MHz are obtained. In the single-pulse regime, a maximum average output power of 204 mW is measured, corresponding to a peak power of 4.2 kW and a pulse energy of 4...
January 15, 2019: Optics Letters
Xiao-Jie Tan, Cihang Kong, Yu-Xuan Ren, Cora S W Lai, Kevin K Tsia, Kenneth K Y Wong
We demonstrate a volumetric two-photon microscopy (TPM) using the non-diffracting Airy beam as illumination. Direct mapping of the imaging trajectory shows that the Airy beam extends the axial imaging range around six times longer than a traditional Gaussian beam does along the propagation direction, while maintaining a comparable lateral width. Benefiting from its non-diffracting nature, the TPM with Airy beam illumination is able not only to capture a volumetric image within a single frame, but also to acquire image structures behind a strongly scattered medium...
January 15, 2019: Optics Letters
Han-Le Zhang, Huan Deng, Jiao-Jiao Li, Min-Yang He, Da-Hai Li, Qiong-Hua Wang
An integral imaging-based 2D/3D convertible display system is proposed by using a lens-array holographic optical element (LAHOE), a polymer dispersed liquid crystal (PDLC) film, and a projector. The LAHOE is closely attached to the PDLC film to constitute a projection screen. The LAHOE is used to realize integral imaging 3D display. When the PDLC film with an applied voltage is in the transparent state, the projector projects a Bragg matched 3D image, and the display system works in 3D mode. When the PDLC film without an applied voltage is in the scattering state, the projector projects a 2D image, and the display system works in 2D mode...
January 15, 2019: Optics Letters
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