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Articles 1 to 20 of 140 Next Page >>


Actively mode-locked Tm3+-doped silica fiber laser with wavelength-tunable, high average output power

  • Christian Kneis, Brenda Donelan, Antoine Berrou, Inka Manek-Hönninger, thierry Robin, Benoit Cadier, Marc Eichhorn, and Christelle Kieleck
  • received 12/17/2014; accepted 03/03/2015; posted 03/03/2015; Doc. ID 230829
  • [full text: PDF (2918) KB)]
  • Abstract: A diode-pumped, actively mode-locked high-power thulium (Tm3+)-doped double-clad silica fiber laser is demonstrated, providing an average output power in mode-locked (continuous wave) operation of 53 W (72 W) with a slope eciency of 34 % (38 %). Mode-locking in the 6th harmonic order was obtained by an acousto-optic modulator driven at 66 MHz without dispersion compensation. The shortest measured output pulse width was 200 ps. Owing to a diffraction grating as cavity end mirror, the central wavelength could be tuned from 1.95 µm to 2.13 µm. The measured beam quality in mode-locked and continuous wave operation has been close to the diffraction-limit.

Keywords (OCIS):

  • (140.3510) Lasers and laser optics : Lasers, fiber
  • (140.3600) Lasers and laser optics : Lasers, tunable
  • (140.4050) Lasers and laser optics : Mode-locked lasers

Time-dependent variation of Fibre Bragg Grating Reflectivity in PMMA based Polymer Optical Fibres

  • David Sáez Rodríguez, David Webb, Kristian Nielsen, and Ole Bang
  • received 12/24/2014; accepted 03/02/2015; posted 03/03/2015; Doc. ID 231329
  • [full text: PDF (1702) KB)]
  • Abstract: In this paper we investigate the effects of viscoelasticity on both the strength and resonance wavelength of two fibre Bragg gratings (FBGs) inscribed in microstructured polymer optical fibre (mPOF) made of undoped PMMA. Both FBGs were inscribed under a strain of 1% in order to increase the material photosensitivity. After the inscription the strain was released and the FBGs spectra were monitored. We initially observed a decrease of the reflection down to zero after which it began to increase. After that, strain tests were carried out to confirm the results and finally the gratings were monitored for a further 120 days, with a stable reflection response being observed beyond 50 days.

Keywords (OCIS):

  • (050.2770) Diffraction and gratings : Gratings
  • (160.5470) Materials : Polymers
  • (060.3735) Fiber optics and optical communications : Fiber Bragg gratings
  • (060.4005) Fiber optics and optical communications : Microstructured fibers
  • (060.5295) Fiber optics and optical communications : Photonic crystal fibers
  • (050.5298) Diffraction and gratings : Photonic crystals

Two-photon-induced Förster resonance energy transfer in a hybrid material engineered from quantum dots and bacteriorhodopsin

  • Victor Krivenkov, igor nabiev, Pavel Samokhvalov, Regina Bilan, Daria Solovyeva, and Alexander Chistyakov
  • received 01/16/2015; accepted 03/02/2015; posted 03/03/2015; Doc. ID 230560
  • [full text: PDF (1043) KB)]
  • Abstract: Energy transfer from nanostructures to biological supramolecular photosystems is an important fundamental issue related to possible influence of nanoobjects on biological functions. We demonstrate here two-photon-induced Förster resonance energy transfer (FRET) from fluorescent CdSe/ZnS quantum dots (QDs) to the photosensitive protein bacteriorhodopsin (bR) in a QD–bR hybrid material. The two-photon absorption cross section of QDs has been found to be about two orders of magnitude larger than that of bR. Therefore, highly selective two-photon excitation of QDs in QD–bR complexes is possible. Moreover, the efficiency of FRET from QDs to bR is sufficient to initiate bR photoconversion through selective two-photon excitation of QDs in the infrared spectral region. The data demonstrate that the effective spectral range in which the bR biological function is excited can be extended beyond the band where the protein itself utilizes light energy. This paves the way to wider applications of QD–bR hybrid materials in photovoltaics, biosensing, and optoelectronics.

Keywords (OCIS):

  • (020.4180) Atomic and molecular physics : Multiphoton processes
  • (260.2160) Physical optics : Energy transfer
  • (160.1435) Materials : Biomaterials
  • (160.4236) Materials : Nanomaterials
  • (160.5335) Materials : Photosensitive materials

Characterization and mitigation of phase modulation dependent loss of liquid crystal on silicon

  • Fu Songnian, Dawei Yu, Hong Zhikun, Ming Tang, Shum Ping, and Dengming Liu
  • received 01/12/2015; accepted 03/02/2015; posted 03/03/2015; Doc. ID 232372
  • [full text: PDF (1271) KB)]
  • Abstract: We characterize the phase modulation dependent loss (PMDL) arising from the commercial liquid crystal on silicon (LCOS) and find that it severely degrades the fidelity of mode selective conversion and orbital angular momentum (OAM) generation, as well as the performance of LCOS-based wavelength selective switch (WSS). For the LP11 mode conversion, an offset-launch technique is proposed to mitigate such effect. For the LPl,m (l >1) mode conversion, the superposition of OAMs with conjugation vortexes is demonstrated to achieve prefect mode conversion. Experimental outcomes verify that both solutions are able to improve the fidelity quality factor by at least 15 dB.

Keywords (OCIS):

  • (060.4510) Fiber optics and optical communications : Optical communications
  • (060.5060) Fiber optics and optical communications : Phase modulation
  • (160.3710) Materials : Liquid crystals
  • (230.6120) Optical devices : Spatial light modulators

Plasmon ruler with gold nanorod dimers: utilizing the second-order resonance

  • Maxim Shcherbakov, Anton Le, Natalia Dubrovina, Anatole Lupu, and Andrey Fedyanin
  • received 12/11/2014; accepted 03/02/2015; posted 03/03/2015; Doc. ID 225798
  • [full text: PDF (734) KB)]
  • Abstract: The idea of utilizing the second-order plasmon resonance of the gold nanorod π-dimers for plasmon rulers is introduced. We report on a qualitatively different dependence of the plasmon resonance shift on the interparticle distance for the first- and second-order longitudinal modes, extending the working range of plasmon rulers up to the distance values of 400 nm.

Keywords (OCIS):

  • (350.4238) Other areas of optics : Nanophotonics and photonic crystals
  • (250.5403) Optoelectronics : Plasmonics
  • (310.6628) Thin films : Subwavelength structures, nanostructures

Fabrication of low-stray-light gratings by broad-beam scanning exposure in the direction perpendicular to the grating grooves

  • Donghan Ma and Zeng Lijiang
  • received 01/20/2015; accepted 03/01/2015; posted 03/03/2015; Doc. ID 232828
  • [full text: PDF (1400) KB)]
  • Abstract: Previous research on making low-stray-light gratings is mainly focused on process steps after the photoresist mask has been made. We propose to improve the quality of the photoresist mask directly in exposure. We present a broad-beam scanning exposure method along the grating vector (i.e. in the direction perpendicular to the grating grooves), utilizing a reference grating clamped below the substrate on the translation stage for phase and attitude locking. Scanning-exposed gratings with a size of 40 × 40 mm2 are successfully made, which have straighter grooves and smoother surfaces, and their stray light levels around the first and second diffraction orders are decreased significantly.

Keywords (OCIS):

  • (050.1950) Diffraction and gratings : Diffraction gratings
  • (050.2770) Diffraction and gratings : Gratings
  • (290.5880) Scattering : Scattering, rough surfaces
  • (290.2648) Scattering : Stray light

Near-Infrared Electro-Optic Modulator Based on Plasmonic Graphene

  • Rongqing Hui, Susobhan Das, Alessandro Salandrino, and Judy Wu
  • received 02/02/2015; accepted 03/01/2015; posted 03/03/2015; Doc. ID 233598
  • [full text: PDF (644) KB)]
  • Abstract: We propose a novel scheme for an electro-optic modulator based on plasmonically enhanced graphene. As opposed to previously reported designs where the switchable absorption of graphene itself was employed for modulation, here a graphene monolayer is used to actively tune the plasmonic resonance condition through the modification of interaction between optical field and an Indium Tin Oxide (ITO) plasmonic structure. Strong plasmonic resonance in the near infrared (NIR) wavelength region can be supported by accurate design of ITO structures, and tuning the graphene chemical potential through electrical gating switches on and off the ITO plasmonic resonance. This provides much increased electro-absorption efficiency as compared to systems relying only on the tunable absorption of the graphene.

Keywords (OCIS):

  • (130.3120) Integrated optics : Integrated optics devices
  • (250.0250) Optoelectronics : Optoelectronics
  • (130.4815) Integrated optics : Optical switching devices
  • (250.5403) Optoelectronics : Plasmonics
  • (130.4110) Integrated optics : Modulators

Nonparaxial accelerating beams with pre-engineered trajectories

  • Nikolaos Efremidis, Raluca Penciu, and Vassilis Paltoglou
  • received 01/08/2015; accepted 03/01/2015; posted 03/03/2015; Doc. ID 232047
  • [full text: PDF (4254) KB)]
  • Abstract: In this letter, we propose a general method for the generation of nonparaxial accelerating beams with arbitrary predefined convex trajectories. We present results for a variety of caustic curves: besides circular, elliptic, and parabolic, we find for the first time power-law and exponential trajectories. In all of these cases the initial required phase is computed in closed form. Furthermore, by changing the initial amplitude we can design different intensity profiles along the caustic.

Keywords (OCIS):

  • (050.1940) Diffraction and gratings : Diffraction
  • (260.2110) Physical optics : Electromagnetic optics
  • (350.5500) Other areas of optics : Propagation
  • (350.7420) Other areas of optics : Waves
  • (070.7345) Fourier optics and signal processing : Wave propagation


Simple way to analyze Brillouin spectra from turbid liquids

  • Mikolaj Pochylski and Jacek Gapiński
  • received 12/12/2014; accepted 02/28/2015; posted 03/03/2015; Doc. ID 230484
  • [full text: PDF (349) KB)]
  • Abstract: The shape of the Brillouin light scattering spectrum recorded from turbid liquids is distinctly distorted compared to that from a transparent sample. The reason for this is the multiple scattering of light within the medium. The usual expression for the Brillouin spectrum does not apply to the multiple scattering situation. In this letter we consider a Brillouin spectrum from opaque samples as composed of a distribution of spectra resulting from elementary scattering events, each occurring in single scattering vector conditions. We introduce a one-parameter test function to define the probability distribution of scattering events occurring at a given value of the scattering vector. The proposed procedure was tested on model liquids being suspensions of sub-micrometer spherical particles of different size and concentration, dispersed in different carrier liquids and studied as a function of temperature. Our analysis made it possible to account for the effect of multiple scattering and to recover the values of mechanical parameters describing the pure solvents.

Keywords (OCIS):

  • (000.2170) General : Equipment and techniques
  • (120.5820) Instrumentation, measurement, and metrology : Scattering measurements
  • (290.4210) Scattering : Multiple scattering
  • (290.5830) Scattering : Scattering, Brillouin
  • (290.7050) Scattering : Turbid media
  • (300.6250) Spectroscopy : Spectroscopy, condensed matter

Reconfigurable dual-channel all-optical logic gate in a silicon waveguide using polarization encoding

  • Shiming Gao, Xiaoyan Wang, Yanqiao Xie, Peiran Hu, and Qiang Yan
  • received 12/11/2014; accepted 02/28/2015; posted 03/03/2015; Doc. ID 230528
  • [full text: PDF (643) KB)]
  • Abstract: A reconfigurable dual-channel all-optical logic gate is proposed and experimentally demonstrated using four-wave mixing in a silicon waveguide for polarization encoding signals. Six logic functions including XNOR, AND, NOR, XOR, AB-, and A-B are implemented at two different wavelength channels by adjusting the polarization states of two 10 Gb/s non-return-to-zero polarization-shift keying (NRZ-PolSK) signals modulated by 10-bit on-off keying (OOK) sequences. The eye diagrams of the logic signals are clearly observed and the logic functions are well demonstrated as the two incident NRZ-PolSK signals are both modulated by OOK sequences originating from 231-1 pseudo random binary sequences.

Keywords (OCIS):

  • (190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
  • (190.4390) Nonlinear optics : Nonlinear optics, integrated optics
  • (230.3750) Optical devices : Optical logic devices

Enhancing near-infrared light absorption in PtSi thin films for Schottky barrier IR detectors using moth-eye surface structures

  • Mike Gordon and Federico Lora Gonzalez
  • received 01/16/2015; accepted 02/28/2015; posted 03/03/2015; Doc. ID 232564
  • [full text: PDF (1225) KB)]
  • Abstract: Si-based Schottky barrier infrared detectors typically use thin (1-10nm) PtSi or Pd₂Si layers grown on Si substrates as an absorption medium. Herein, we demonstrate the use of sub-wavelength moth-eye (ME) structures on the Si substrate of such detectors to enhance absorption of near infrared (NIR) light in the active PtSi layer to increase detector efficiency. Absorbance enhancement of 70-200% in the λ=1-2.5μm range is demonstrated in crystalline PtSi films grown via electron beam evaporation of Pt and subsequent vacuum annealing. Low total reflectance (<10%) was measured for ME films, demonstrating the efficacy of the moth-eye effect. Effective medium approximation calculations show that absorption enhancement at short wavelengths is partly due to forward scattering, which increases the effective optical path length in PtSi. Results also suggest that moth-eye structuring of substrates is a general and low-cost method to enhance absorption in a variety of IR material platforms used for back-illuminated detectors.

Keywords (OCIS):

  • (040.3060) Detectors : Infrared
  • (040.6040) Detectors : Silicon
  • (310.1210) Thin films : Antireflection coatings
  • (290.2558) Scattering : Forward scattering
  • (310.6628) Thin films : Subwavelength structures, nanostructures

Brewster effect in metafilms composed of bi-anisotropic split-ring resonators

  • Yasuhiro Tamayama
  • received 02/06/2015; accepted 02/28/2015; posted 03/03/2015; Doc. ID 234080
  • [full text: PDF (427) KB)]
  • Abstract: The Brewster effect is extended to single-layer metafilms. In contrast to bulk media, the Brewster effect in metafilms can be realized by tailoring the radiation pattern of a distribution of meta-atoms rather than the effective medium parameters. A metafilm composed of bi-anisotropic split-ring resonators is designed based on the theory, and its characteristics are numerically analyzed. The simulation demonstrates that there exists a condition for which the reflected wave becomes vertically polarized regardless of the incident polarization.

Keywords (OCIS):

  • (230.5440) Optical devices : Polarization-selective devices
  • (260.2110) Physical optics : Electromagnetic optics
  • (160.3918) Materials : Metamaterials

Swept optical SSB-SC modulation technique for high-resolution large-dynamic-range static strain measurement using FBG-FP sensors

  • Wentao Zhang, wenzhu huang, and Fang Li
  • received 12/05/2014; accepted 02/27/2015; posted 03/03/2015; Doc. ID 229133
  • [full text: PDF (663) KB)]
  • Abstract: This paper presents a static strain demodulation technique for FBG-FP sensors using a suppressed carrier LiNbO3 (LN) optical single sideband (SSB-SC) modulator. A narrow-linewidth tunable laser source is generated by driving the modulator using a linear chirp signal. Then this tunable single-frequency laser is used to interrogate the FBG-FP sensors with Pound-Drever-Hall (PDH) technique, which is beneficial to eliminate the influence of light intensity fluctuation of the modulator at different tuning frequency. The static strain is demodulated by calculating the wavelength difference of the PDH signals between the sensing FBG-FP sensor and the reference FBG-FP sensor. As an experimental result using the modulator, the linearity (R2) of the time-frequency response increases from 0.989 to 0.997 and the frequency-swept range (dynamic range) increases from hundreds of MHz to several GHz compared with commercial PZT-tunable laser. The high-linearity time-wavelength relationship of the modulator is benefit for improving the strain measurement resolution as it can solve the problem of the frequency-swept nonlinearity effectively. In the laboratory test, a 0.67-nanostrain static-strain resolution, with a 6-GHz dynamic range, is demonstrated.

Keywords (OCIS):

  • (060.2370) Fiber optics and optical communications : Fiber optics sensors
  • (060.4080) Fiber optics and optical communications : Modulation
  • (060.5060) Fiber optics and optical communications : Phase modulation
  • (060.3735) Fiber optics and optical communications : Fiber Bragg gratings

40-GHz photonic waveform generator by linear shaping of four spectral sidebands

  • Christophe Finot
  • received 01/05/2015; accepted 02/27/2015; posted 02/27/2015; Doc. ID 231924
  • [full text: PDF (899) KB)]
  • Abstract: We show that amplitude and phase shaping of only four sidebands of the optical spectrum is sufficient to synthesize parabolic, triangular or flat-top pulse trains at a repetition rate of 40 GHz. Selection of the waveform is easily achieved by changing the phase difference between the inner and outer spectral lines. Experimental results confirm the high quality of the intensity profiles that are obtained.

Keywords (OCIS):

  • (230.6120) Optical devices : Spatial light modulators
  • (320.5540) Ultrafast optics : Pulse shaping

Reconfigurable non-blocking 4-port silicon thermo-optic optical router based on Mach-Zehnder optical switches

  • Lin Yang, Yuhao Xia, Fanfan Zhang, Qiaoshan Chen, Ping Zhou, Lei Zhang, and jianfeng ding
  • received 02/03/2015; accepted 02/26/2015; posted 02/26/2015; Doc. ID 233679
  • [full text: PDF (1595) KB)]
  • Abstract: We demonstrate a reconfigurable non-blocking 4-port silicon thermo-optic optical router based on MZ optical switches. For all optical links in its 9 routing states, the optical SNRs are larger than 15 dB in the wavelength range from 1525 nm to 1565 nm. The optical router can manipulate 50 wavelength-division-multiplexing channels with the data rate of 32 Gbps for each channel in the same wavelength range. Its average energy efficiency is about 16.3 fJ/bit and its response time is about 26 μs.

Keywords (OCIS):

  • (200.4650) Optics in computing : Optical interconnects
  • (230.3120) Optical devices : Integrated optics devices
  • (130.4815) Integrated optics : Optical switching devices

Strong Enhancement of Nano-sized Circularly Polarized Light using an Aperture Antenna with V-groove Structures

  • Yongfu Cai, Soushi Ikeda, Katsuji Nakagawa, Hiroshi Kikuchi, Naoki Shimizu, and Takayuki Ishibashi
  • received 02/12/2015; accepted 02/26/2015; posted 03/03/2015; Doc. ID 234611
  • [full text: PDF (754) KB)]
  • Abstract: We present a new type of aperture antenna with V-groove structures that are made of Au to enhance strong circularly polarized light (CPL). Simulations using the finite element method revealed that strong CPL was enhanced within the aperture with a diameter of 10 nm. The intensity of the electric field was enhanced and was 22700 times greater than that of the incident light. The channel plasmon polaritons generated in the V-groove structures were responsible for the strong enhancement. The influence of the angle and length of the V-groove on the enhancement of the CPL was investigated.

Keywords (OCIS):

  • (240.6680) Optics at surfaces : Surface plasmons
  • (260.3910) Physical optics : Metal optics
  • (260.5430) Physical optics : Polarization

Determining vortex densities of random non-diffracting beams

  • Cheng-Shan Guo, Ben-Yi Wang, Xiao-Lu Ge, and Qing-Yang Yue
  • received 12/11/2014; accepted 02/25/2015; posted 02/27/2015; Doc. ID 230566
  • [full text: PDF (700) KB)]
  • Abstract: We analyzed the evolution and the statistical properties of the optical vortices existed in a random non-diffracting beam (RNDB). Through simulating the evolution of the phase singularities (PSs) of the optical vortices in a RNDB when its ring shaped spatial spectrum is set to possess different phase fluctuations, we found that the optical vortices of the RNDBs can be considered to originate from the zero rings of the Bessel beams with the same ring-shaped structure of the spatial spectrum (but with zero phase fluctuations), and so the average vortex density or the PS density will be determined by the average duration of the zero rings of the corresponding Bessel function. According to this model, we successfully derived, for the first time to our knowledge, an analytical formula for quantitatively predicting the vortex density of the RNDBs. This formula could be helpful for understanding and designing the RNDBs with specific vortex density, and significant in the applications of fabricating photonic crystals based on the RNDBs.

Keywords (OCIS):

  • (050.1970) Diffraction and gratings : Diffractive optics
  • (070.3185) Fourier optics and signal processing : Invariant optical fields
  • (050.4865) Diffraction and gratings : Optical vortices

Compact fiber optic curvature sensors based on super-mode interference in a seven core fiber

  • Guillermo Salceda, Amy Van Newkirk, Jose Antonio-Lopez, Alejandro Martínez-Rios, Axel Schulzgen, and Rodrigo Amezcua
  • received 12/19/2014; accepted 02/25/2015; posted 02/27/2015; Doc. ID 231103
  • [full text: PDF (1576) KB)]
  • Abstract: A compact, low loss, and highly sensitive optical fiber curvature sensor is presented. The device consists of a few-millimeter-long piece of seven-core fiber spliced between two single mode fibers. When the optical fiber device is kept straight, a pronounced interference pattern appears in the transmission spectrum. However, when the device is bent, a spectral shift of the interference pattern is produced and the visibility of the interference notches changes. This allows for using either visibility or spectral shift for sensor interrogation. The dynamic range of the device can be tailored through the proper selection of the length of the seven core fiber. The effects of temperature and refractive index of the external medium on the response of the curvature sensor are also discussed. Linear sensitivity of about 3000 nm/mm-1 for bending was observed experimentally

Keywords (OCIS):

  • (060.2280) Fiber optics and optical communications : Fiber design and fabrication
  • (060.2370) Fiber optics and optical communications : Fiber optics sensors

Nanobump microresonator

  • Misha Sumetsky and Leonid Kochkurov
  • received 01/29/2015; accepted 02/25/2015; posted 02/27/2015; Doc. ID 233557
  • [full text: PDF (493) KB)]
  • Abstract: We introduce a whispering gallery mode (WGM) nanobump microresonator (NBMR) and develop its theory. This microresonator is formed by an asymmetric nanoscale-high deformation of the translationally symmetric optical fiber surface, which is employed in fabrication of Surface Nanoscale Axial Photonics (SNAP) structures. It is shown that an NBMR causes strong localization of WGMs near a closed ray (geodesic) at the fiber surface, provided that this ray is stable. Our theory explains and describes the experimentally observed localization of WGMs by NBMRs and is useful for the design and fabrication of SNAP devices.

Keywords (OCIS):

  • (060.2340) Fiber optics and optical communications : Fiber optics components
  • (230.3990) Optical devices : Micro-optical devices
  • (140.3945) Lasers and laser optics : Microcavities

In vivo optical resolution photoacoustic microscopy using glancing angle deposited nanostructured Fabry-Perot etalons

  • Parsin Haji Reza, Roger Zemp, Michael Brett, and Jason Sorge
  • received 11/26/2014; accepted 02/25/2015; posted 02/25/2015; Doc. ID 228590
  • [full text: PDF (552) KB)]
  • Abstract: In this letter, reflection mode optical resolution photoacoustic microscopy (OR-PAM) using glancing angle deposited (GLAD) nanostructured Fabry-Perot interferometers (FPI) for in vivo applications is reported. GLAD is a single-step physical vapor-deposition (PVD) technique used to fabricate porous nanostructured thin films. Using titanium dioxide, a transparent semiconductor with a high refractive index (n = 2.4), the GLAD technique can be employed to fabricate samples with tailored nano-porosity, refractive index periodicities, and high Q-factor reflectance spectra. The OR-PAM in vivo images of CAM-membrane of 5-day chicken embryo model are demonstrated. The phantom study shows lateral resolution and signal to noise ratio better than 7µm and 35dB respectively. The sensitive GLAD FPI allows photoacoustic imaging down to a few nJ pulse energy. To the best of our knowledge, this is the first time that an optical resolution reflection mode photoacoustic imaging technique using optical detection is demonstrated for in vivo applications.

Keywords (OCIS):

  • (170.3880) Medical optics and biotechnology : Medical and biological imaging
  • (170.5120) Medical optics and biotechnology : Photoacoustic imaging
  • (180.0180) Microscopy : Microscopy
  • (180.5810) Microscopy : Scanning microscopy
  • (170.1065) Medical optics and biotechnology : Acousto-optics

Articles 1 to 20 of 140 Next Page >>

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