Broadband Beam Splitter Research Articles

Configurable lossless broadband beam splitters for semi-guided waves in integrated silicon photonics

We show that narrow trenches in a high-contrast silicon-photonics slab can act as lossless power dividers for semi-guided waves. Reflectance and transmittance can be easily configured by selecting the trench width. At sufficiently high angles of incidence, the devices are lossless, apart from material attenuation and scattering due to surface roughness. We numerically simulate a series of devices within the full 0-to-1-range of splitting ratios, for semi-guided plane wave incidence as well as for excitation by focused Gaussian wave bundles. Straightforward cascading of the trenches leads to concepts for 1×M-power dividers and a polarization beam splitter.

Multidimensional Image and Beam Splitter Based on Hyperbolic Metamaterials.

Recently, multidimensional metasurfaces, which can modulate multiple optical parameters of input and output lights simultaneously, have aroused intensive interest. Here, we demonstrate multidimensional switchable images and 3D integrated beam splitters based on hyperbolic metamaterials (HMMs). On one hand, a switchable image controlled by output helicity and input wavelengths is achieved by arranging HMMs with different polarization conversion performance. On the other hand, polarization-multiplexed broadband beam splitter is generated by spatially engineering the subunit with broadband half-plate performance. By integrating the multiplexed beam splitter with a filter metamaterial, this multidimensional beam splitter can further realize the separation of output light by space and wavelength. This cascaded multilayer metamaterial achieves a brand new optical functionality and offers more inspiring possibilities for the design of multifunctional optical devices in the future.

Metasurface-enabled broadband beam splitters integrated with quarter-wave plate functionality.

Conventional beam splitters and wave plates, while being essential components in diverse optical systems, require considerable space, especially when used in combination. Here, we designed and experimentally demonstrated metasurface-enabled efficient broadband beam splitters integrated with quarter-wave plate (QWP) functionality for simultaneous power splitting and circular-to-linear polarization conversion in the near-infrared range. By utilizing two different gap-plasmon meta-atoms, which function as QWPs performing efficient circular-to-linear polarization conversion and provide the phase difference of π between reflected linearly polarized beams, we designed a metasurface that completely suppress the specular reflection (zero-order diffraction) and second-order diffraction, while ensuring efficient and equal beam splitting of a circularly polarized wave into two reflected beams with predesigned directions and well-defined linear-polarization states in the wavelength range of 750-950 nm. The fabricated metasurface exhibits excellent performance of circular-to-linear conversion and power splitting, with efficient suppression of specular reflection (<1%) and splitting efficiencies above 50% for both right and left circularly polarized excitation at the design wavelength of λ = 850 nm. By enabling the combined functionalities of a conventional beam splitter and a QWP, our approach opens up new prospects for advanced research and applications targeting photonics integration and miniaturization.

Design and Simulation of Broadband Beam Splitter on a Silicon Nitride Platform for Optical Coherence Tomography

ABSTRACTIntegrated photonics enables the miniaturization of bulk optical components for biosensing applications such as optical coherence tomography (OCT) and is therefore promising for future lab-on-chip solutions. Here, we report the design and simulation of a compact low loss broadband beam splitter with arbitrary coupling ratios on silicon nitride platform for OCT systems. The reported coupler uses asymmetric waveguide-based phase control section for 10:90, 20:80, 30:70, 40:60, and 50:50 splitting ratios and is broadband over 100 nm with the central wavelength of 850 nm. The couplers are realized for transverse electric, transverse magnetic, and fully vectorial modes, and maximum excess loss for all mode types is reported to be less than 0.19 dB. The design tolerance of waveguide width and thickness of the designed coupler is further calculated and is within fabrication limit.

Control of adiabatic light transfer in coupled waveguides with longitudinally varying detuning

We study adiabatic light transfer in systems of two coupled waveguides with spatially varying detuning of the propagation constants, providing an analogy to the quantum phenomena of rapid adiabatic passage (RAP) and two-state stimulated Raman adiabatic passage (two-state STIRAP). Experimental demonstration using a photoinduction technique confirms the robust and broadband character of the structures that act as broadband directional couplers and broadband beam splitters, respectively.

Second-harmonic frequency-resolved optical gating covering two and a half optical octaves using a single spectrometer

We report the measurement of laser pulse shapes covering the range 580–3250 nm using second-harmonic generation frequency-resolved optical gating equipped with a single inexpensive visible-NIR miniature spectrometer and a single pair of homemade broadband beam splitters. Our experimental scheme exploits frequency up-conversion by BBO crystals and appropriate corrections for dispersion, beam splitter filtering and phase-matching efficiency. The signal and idler waves from a commercial optical parametric amplifier pumped by a Ti:Sapphire laser (26 fs, 1 kHz) have been characterized as well as their second harmonic. The pulse shapes out of a commercial difference frequency generation module mixing signal and idler have also been measured up to 3250 nm. The resulting pulses range from 20 to 120 fs, and their chirp characteristics are also exposed. Our approach is demonstrated over most of the doubling crystal transparency range.

Simulation and Experiment of Speckle Reduction by the Beam Splitting Method on a Pico-Projection System

An optical scheme using two correlationless beams to suppress the speckle of the pico-projection system is proposed. By using two broadband beam splitters (BBS) and two high reflection mirrors, the originally incident laser beam is split into two beams. The mutual correlation coefficient between two split beams is very close to zero. We use the haze reflection based on the random scattering model to simulate light reflected from the rough surface. In simulations, light is respectively reflected from the same size flat and rough surfaces and both recorded images are compared with each other. The image from flat surface is very clear on the detector plane. On the contrary, the image from rough surface is very fuzzy and the edge is hard to figure out. The simulations show that the speckle contrast ratio (CR) is reduced from 1.0 to 0.707. We find out a solution of the speckleCRless than 0.71 when the distance between two BBSs is 2.4 mm and the thickness of each BBS is 0.4 mm. Finally, we carry out an experiment and verify the simulating results. By our analysis from the experimental data, the speckleCRcan be reduced about 25% which is close to the theoretical value of 29.3%.

Broad band beam splitter based on the double-groove fused silica grating

In this paper, we propose a broad band 1×3 beam splitter operating in the telecommunication wavelength band under normal incidence, this device consisting of a double-groove fused silica grating layer is designed with using the inverse mathematical method and rigorous vector diffraction theory. It is shown from our calculations that the device presents excellent beam splitter ability for TE polarization light with the average diffraction efficiencies is more than 95% over ∼100nm wavelength range, moreover, the uniformity of our beam splitter is better than 2% in the whole wavelength band. Furthermore, the physical understanding of the diffraction behaviors taking place inside the beam splitter gratings can be explained by the modal method.

Double-structure, bidirectional and polarization-independent subwavelength grating beam splitter

A novel broadband beam splitter (BS) at a wavelength of 1.55 μm is proposed and demonstrated, which is based on the form birefringence of subwavelength binary blazed grating and effective-medium theory. Rigorous coupled-wave analysis (RCWA) is used to optimize the design of this beam splitter. In order to achieve high coupling efficiency and equal power separation, the grating depth, period and wavelength are optimized, and the double-structure design which consists of symmetrical subwavelength gratings is adopted. Finally, the additional reflectors are also discussed and analyzed. Simulation results for TE polarized wave and TM polarized wave are presented. Using three reflectors, the BS for TE light are designed to split incident light beam into two beams of nearly equal power (41% and 43%), and the power difference of two output ports is less than 3% over a 20 nm wavelength bandwidth range. Simultaneously, the coupling efficiency of TM model for the right and the left branches of waveguide are 33% and 40%, respectively. The power differences of two ports of waveguide are lower than 10% with 80 nm wavelength bandwidth. Both theoretical analysis and simulation results show that the beam splitter designed here has advantages of high coupling efficiency, compact structure and polarization independence.

High Efficient Subwavelength Binary Blazed Grating Beam Splitter via Vertical Coupling

We propose a novel broadband beam splitter (BS) with a single-layer and compact grating vertical coupling structure, which is based on the form birefringence of subwavelength binary blazed grating and effective-medium theory. Rigorous coupled-wave analysis is used to optimize the design of this beam splitter. The simulation and analysis show that the BS for transverse electric (TE) light are designed to split the incident light beam into two beams of equal power (nearly 50% split), which travel in opposite directions in the waveguide. The coupling length is about 9 . The coupling efficiency for the right and the left branches of waveguide are 47% and 52%, respectively. The power difference of two output ports is less than 15% over a 75-nm wavelength bandwidth range.

New multichannel kinetic spectrophotometer–fluorimeter with pulsed measuring beam for photosynthesis research

A multichannel kinetic spectrophotometer-fluorimeter with pulsed measuring beam and differential optics has been constructed for measurements of light-induced absorbance and fluorescence yield changes in isolated chlorophyll-proteins, thylakoids and intact cells including algae and photosynthetic bacteria. The measuring beam, provided by a short (2 micros) pulse from a xenon flash lamp, is divided into a sample and reference channel by a broad band beam splitter. The spectrum in each channel is analyzed separately by a photodiode array. The use of flash measuring beam and differential detection yields high signal-to-noise ratio (noise level of 2 x 10(-4) in absorbance units per single flash) with negligible actinic effect. The instrument covers a spectral range between 300 and 1050 nm with a spectral resolution of 2.1, 6.4 or 12.8 nm dependent on the type of grating used. The optical design of the instrument enables measuring of the difference spectra during an actinic irradiation of samples with continuous light and/or saturation flashes. The time resolution of the spectrophotometer is limited by the length of Xe flash lamp pulses to 2 micros.

Determination and analysis of non-linear index profiles in electron-beam-deposited MgOAl2O3ZrO2 ternary composite thin-film optical coatings

Thickness-dependent index non-linearity in thin films has been a thought provoking as well as intriguing topic in the field of optical coatings. The characterization and analysis of such inhomogeneous index profiles pose several degrees of challenges to thin-film researchers depending upon the availability of relevant experimental and process-monitoring-related information. In the present work, a variety of novel experimental non-linear index profiles have been observed in thin films of MgOAl2O3ZrO2 ternary composites in solid solution under various electron-beam deposition parameters. Analysis and derivation of these non-linear spectral index profiles have been carried out by an inverse-synthesis approach using a real-time optical monitoring signal and post-deposition transmittance and reflection spectra. Most of the non-linear index functions are observed to fit polynomial equations of order seven or eight very well. In this paper, the application of such a non-linear index function has also been demonstrated in designing electric-field-optimized high-damage-threshold multilayer coatings such as normal- and oblique-incidence edge filters and a broadband beam splitter for p-polarized light. Such designs can also advantageously maintain the microstructural stability of the multilayer structure due to the low stress factor of the non-linear ternary composite layers.

High-throughput, high-damage-threshold broadband beam splitter for high-order harmonics in the extreme-ultraviolet region.

We demonstrate a high-throughput and high-damage-threshold beam splitter for high-order harmonics in the soft-x-ray region that uses Si and (or) SiC plates set at Brewster's angle with respect to the pump wavelength. The beam splitters are guaranteed to have a damage threshold of at least 0.8 TW/cm2 (average power density, 0.25 W/cm2) and an attenuation rate of 10(-4)-10(-5) for a 30-fs pump pulse. The measured reflection efficiency at the 27th harmonic (29.6 nm) was 0.56 for Si and 0.45 for SiC. These beam splitters are useful not only for high harmonics but also for longitudinally pumped x-ray lasers.

A broad-band beamsplitter

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text I. S. Gainutdinov, E. A. Nesmelov, R. S. Sabirov , and R. G. Safin, "A broad-band beamsplitter," J. Opt. Technol. 69, 276- (2002) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Achromatic fan-out diffractive system for white-light free-space optical interconnects

A simple and versatile white-light fan-out diffractive system based on the achromatization of the fractional Talbot effect is proposed. This achromatic configuration is able to interconnect a single polychromatic point source with a 2-D array of optoelectronic microdevices with low residual chromatic aberration even for white light. The whole broadband beamsplitter system is formed by two simple diffractive optical elements, a periodic diffractive lenslet array and a diffractive lens, that are made with a direct laser writing technique giving high light efficiency. The focal amplitude distribution corresponding to the lenslet array produces, by free-space propagation, self-replicas with different density of light points. These patterns, in conjunction with the achromatization process carried out by the additional diffractive lens, are, in short, the key to achieving a set of undistorted white-light spots at the output plane with high uniformity and variable separation between them. Experimental results are also shown.

Artificial diamond as a broadband infrared beam splitter for Fourier transform spectroscopy

We show that an artificially grown diamond plate serves as a very broadband beam splitter from approximately 7 mum, where the intrinsic diamond absorption becomes important, to the submillimeter region (a 250-mum wavelength or longer).