Photonics

2791 KiB

Open AccessArticle

Extraordinary Light-Trapping Enhancement in Silicon Solar Cell Patterned with Graded Photonic Super-Crystals

by Safaa Hassan, David Lowell, Murthada Adewole, David George, Hualiang Zhang and Yuankun Lin

Photonics 2017, 4(4), 50; https://doi.org/10.3390/photonics4040050 - 20 Dec 2017

Cited by 11 | Viewed by 4107

Light-trapping enhancement in newly discovered graded photonic super-crystals (GPSCs) with dual periodicity and dual basis is herein explored for the first time. Broadband, wide-incident-angle, and polarization-independent light-trapping enhancement was achieved in silicon solar cells patterned with these GPSCs. These super-crystals were designed by [...] Read more.

Light-trapping enhancement in newly discovered graded photonic super-crystals (GPSCs) with dual periodicity and dual basis is herein explored for the first time. Broadband, wide-incident-angle, and polarization-independent light-trapping enhancement was achieved in silicon solar cells patterned with these GPSCs. These super-crystals were designed by multi-beam interference, rendering them flexible and efficient. The optical response of the patterned silicon solar cell retained Bloch-mode resonance; however, light absorption was greatly enhanced in broadband wavelengths due to the graded, complex unit super-cell nanostructures, leading to the overlap of Bloch-mode resonances. The broadband, wide-angle light coupling and trapping enhancement mechanism are understood to be due to the spatial variance of the index of refraction, and this spatial variance is due to the varying filling fraction, the dual basis, and the varying lattice constants in different directions. Full article

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(a) Schematic of a silicon photovoltaic device patterned with a GPSC on a silicon (Si) absorbing layer. (b) Permittivity structures output from MIT Electromagnetic Equation Propagation (MEEP) simulation with a unit super-cell size of 12a × 12a (a = 350 nm, the red region is silicon and the blue region is ITO). (c) SEM of a fabricated GPSC in PMMA using e-beam lithography. (d) A unit super-cell size of 6a × 6a (a = 350 nm) formed by eight-beam interference with a threshold intensity Ith that is 30% of the maximum. (d) An eight-beam interference pattern with a unit super-cell of 6a × 6a (a = 350 nm). The dashed squares link lattices at corners that belong to one set of graded lattice. (e) Absorption spectra for silicon patterned with GPSC with a unit cell of 6a × 6a, and with a traditional photonic crystal with a unit cell size of 350 × 350 nm2 with silicon and a circle of ITO with a 145 nm diameter in the center. The dashed green line indicates the baseline of absorption for eye guidance. Full article ">Figure 2
(a) Absorption versus wavelength profile at normal incidence for the silicon patterned with two GPSCs with a unit super-cell size of 12a × 12a: a GPSC of threshold intensity Ith = 35% (a) and a GPSC of threshold intensity Ith = 52% (b). Full article ">Figure 3
(a–d) Absorption spectra versus wavelength for 500-nm-thick silicon patterned with GPSC with a unit super-cell of 12a × 12a (a = 350 nm) and with a threshold intensity of 35% of maximum with [1, 0] polarized light at normal incidence, compared with the absorption spectrum at four off-normal angles of incidence (zenith angle = 10°, 20°, 30°, and 45°, respectively) with s-polarization. The absorption from the silicon patterned with the GPSC at an incident angle of 30° with p-polarization is also shown in (c). Full article ">Figure 4
(a) Absorption spectra of light with polarizations in the [1, 0] and [1, 1] directions incident on silicon patterned with a GPSC with a unit super-cell of 12a × 12a (a = 350 nm), formed with a threshold of 35% of the maximum interference intensity. (b) Absorption spectra of light with polarizations in the [1, 0] direction incident on silicon patterned with a GPSC with a unit super-cell of 6a × 6a (a = 350 nm), formed with a threshold of 30% of the maximum intensity for the pattern from the L and H regions in (c). (c) Eight-beam interference pattern with a unit super-cell size 6a × 6a, showing two distinct regions, marked with an L (L for low intensity spot in the center) and an H (H for high intensity spot in the center). Full article ">Figure 5
(a) Cross-section in the x-z plane of the eight-beam interference pattern. (b) Cross section in the x-y plane of the eight-beam interference patterned as viewed at the location indicated by the red line in (a). The pattern becomes the one in (c) when the phases of four outer interference beams are set to be (0, 0.15π, 0, 0.15π). Full article ">

4068 KiB

Open AccessFeature PaperReview

Microwave Signal Processing over Multicore Fiber

by Sergi García, David Barrera, Javier Hervás, Salvador Sales and Ivana Gasulla

Photonics 2017, 4(4), 49; https://doi.org/10.3390/photonics4040049 - 8 Dec 2017

Cited by 8 | Viewed by 5698

Abstract

We review the introduction of the space dimension into fiber-based technologies to implement compact and versatile signal processing solutions for microwave and millimeter wave signals. Built upon multicore fiber links and devices, this approach allows the realization of fiber-distributed signal processing in the [...] Read more.

We review the introduction of the space dimension into fiber-based technologies to implement compact and versatile signal processing solutions for microwave and millimeter wave signals. Built upon multicore fiber links and devices, this approach allows the realization of fiber-distributed signal processing in the context of fiber-wireless communications, providing both radiofrequency access distribution and signal processing in the same fiber medium. We present different space-division multiplexing architectures to implement tunable true time delay lines that can be applied to a variety of microwave photonics functionalities, such as signal filtering, radio beamsteering in phased array antennas or optoelectronic oscillation. In particular, this paper gathers our latest work on the following multicore fiber technologies: dispersion-engineered heterogeneous multicore fiber links for distributed tunable true time delay line operation; multicavity devices built upon the selective inscription of gratings in homogenous multicore fibers for compact true time delay line operation; and multicavity optoelectronic oscillation over both homogeneous and heterogeneous multicore fibers. Full article

(This article belongs to the Special Issue Microwave Photonics 2017)

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315 KiB

Open AccessArticle

Higher-Order Interactions in Quantum Optomechanics: Analytical Solution of Nonlinearity

by Sina Khorasani

Photonics 2017, 4(4), 48; https://doi.org/10.3390/photonics4040048 - 5 Dec 2017

Cited by 8 | Viewed by 4011

Abstract

A method is described to solve the nonlinear Langevin equations arising from quadratic interactions in quantum mechanics. While the zeroth order linearization approximation to the operators is normally used, here, first and second order truncation perturbation schemes are proposed. These schemes employ higher-order [...] Read more.

A method is described to solve the nonlinear Langevin equations arising from quadratic interactions in quantum mechanics. While the zeroth order linearization approximation to the operators is normally used, here, first and second order truncation perturbation schemes are proposed. These schemes employ higher-order system operators, and then approximate number operators with their corresponding mean boson numbers only where needed. Spectral densities of higher-order operators are derived, and an expression for the second-order correlation function at zero time-delay has been found, which reveals that the cavity photon occupation of an ideal laser at threshold reaches

\sqrt{6} - 2

, in good agreement with extensive numerical calculations. As further applications, analysis of the quantum anharmonic oscillator, calculation of Q-functions, analysis of quantum limited amplifiers, and nondemoliton measurements are provided. Full article

7108 KiB

Open AccessArticle

Heat Dissipation Schemes in AlInAs/InGaAs/InP Quantum Cascade Lasers Monitored by CCD Thermoreflectance

by Dorota Pierścińska, Kamil Pierściński, Piotr Gutowski, Mikołaj Badura, Grzegorz Sobczak, Olga Serebrennikova, Beata Ściana, Marek Tłaczała, Grzegorz Sobczak and Maciej Bugajski

Photonics 2017, 4(4), 47; https://doi.org/10.3390/photonics4040047 - 3 Dec 2017

Cited by 15 | Viewed by 5476

Abstract

In this paper, we report on the experimental investigation of the thermal performance of lattice matched AlInAs/InGaAs/InP quantum cascade lasers. Investigated designs include double trench, single mesa, and buried heterostructures, which were grown by combined Molecular Beam Epitaxy (MBE) and Metal Organic Vapor [...] Read more.

In this paper, we report on the experimental investigation of the thermal performance of lattice matched AlInAs/InGaAs/InP quantum cascade lasers. Investigated designs include double trench, single mesa, and buried heterostructures, which were grown by combined Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) techniques. The thermal characteristics of lasers are investigated by Charge-Coupled Device CCD thermoreflectance. This method allows for the fast and accurate registration of high-resolution temperature maps of the whole device. We observe different heat dissipation mechanisms for investigated geometries of Quantum Cascade Lasers (QCLs). From the thermal point of view, the preferred design is the buried heterostructure. The buried heterostructures structure and epi-layer down mounting help dissipate the heat generated from active core of the QCL. The experimental results are in very good agreement with theoretical predictions of heat dissipation in various device constructions. Full article

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1995 KiB

Open AccessFeature PaperReview

Integrated Microwave Photonics for Wideband Signal Processing

by Xiaoke Yi, Suen Xin Chew, Shijie Song, Linh Nguyen and Robert Minasian

Photonics 2017, 4(4), 46; https://doi.org/10.3390/photonics4040046 - 30 Nov 2017

Cited by 36 | Viewed by 7411

Abstract

We describe recent progress in integrated microwave photonics in wideband signal processing applications with a focus on the key signal processing building blocks, the realization of monolithic integration, and cascaded photonic signal processing for analog radio frequency (RF) photonic links. New developments in [...] Read more.

We describe recent progress in integrated microwave photonics in wideband signal processing applications with a focus on the key signal processing building blocks, the realization of monolithic integration, and cascaded photonic signal processing for analog radio frequency (RF) photonic links. New developments in integration-based microwave photonic techniques, that have high potentialities to be used in a variety of sensing applications for enhanced resolution and speed are also presented. Full article

(This article belongs to the Special Issue Microwave Photonics 2017)

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Measured responses of the microwave photonics (MWP) phase shifter where the different colour lines show the phase shifter operation as the carrier is tuned from 1554.30 nm to 1554.55 nm (a) continuous radio frequency (RF) phase tuning (b) superimposed RF power variations at various RF phase shifts. Inset: Optical response of the phase shifter. Full article ">Figure 2
(a) Schematic of eye-like ring resonator delay line with unbalanced temperature-controlled Mach Zehnder Interferometer (MZI) power splitter. (b) The dependence of the through port group delay τg and optical power transmission |HR|2 on field coupling ratio κ1 or 2 in (b) fast light and (c) slow light regimes. Full article ">Figure 3
(a) Schematics and (b) illustration of the proposed single passband microwave photonic filter (SPMPF). Full article ">Figure 4
(a) Schematic diagram of the integrated optoelectronic oscillators (OEO)-based temperature sensor. PM: phase modulator; EDFA: Erbium doped fiber amplifier; EA: electronic amplifier; PC: polarization controller; ESA: electrical spectrum analyser. Experimental results after closing the OEO loop (b) Measured RF response at 24.78 °C. Inset: Zoomed-in response of the RF oscillation mode. (c) Measured RF oscillation frequency shift with temperature variations (d) Measured oscillation frequency shift as a function of the temperature Full article ">Figure 4 Cont.
(a) Schematic diagram of the integrated optoelectronic oscillators (OEO)-based temperature sensor. PM: phase modulator; EDFA: Erbium doped fiber amplifier; EA: electronic amplifier; PC: polarization controller; ESA: electrical spectrum analyser. Experimental results after closing the OEO loop (b) Measured RF response at 24.78 °C. Inset: Zoomed-in response of the RF oscillation mode. (c) Measured RF oscillation frequency shift with temperature variations (d) Measured oscillation frequency shift as a function of the temperature Full article ">Figure 5
Schematic diagram of the distributed optical signal processing MWP subsystem with cascaded functionalities. Full article ">

4542 KiB

Open AccessReview

Tunable Multiband Microwave Photonic Filters

by Mable P. Fok and Jia Ge

Photonics 2017, 4(4), 45; https://doi.org/10.3390/photonics4040045 - 23 Nov 2017

Cited by 31 | Viewed by 8307

Abstract

The increasing demand for multifunctional devices, the use of cognitive wireless technology to solve the frequency resource shortage problem, as well as the capabilities and operational flexibility necessary to meet ever-changing environment result in an urgent need of multiband wireless communications. Spectral filter [...] Read more.

The increasing demand for multifunctional devices, the use of cognitive wireless technology to solve the frequency resource shortage problem, as well as the capabilities and operational flexibility necessary to meet ever-changing environment result in an urgent need of multiband wireless communications. Spectral filter is an essential part of any communication systems, and in the case of multiband wireless communications, tunable multiband RF filters are required for channel selection, noise/interference removal, and RF signal processing. Unfortunately, it is difficult for RF electronics to achieve both tunable and multiband spectral filtering. Recent advancements of microwave photonics have proven itself to be a promising candidate to solve various challenges in RF electronics including spectral filtering, however, the development of multiband microwave photonic filtering still faces lots of difficulties, due to the limited scalability and tunability of existing microwave photonic schemes. In this review paper, we first discuss the challenges that were facing by multiband microwave photonic filter, then we review recent techniques that have been developed to tackle the challenge and lead to promising developments of tunable microwave photonic multiband filters. The successful design and implementation of tunable microwave photonic multiband filter facilitate the vision of dynamic multiband wireless communications and radio frequency signal processing for commercial, defense, and civilian applications. Full article

(This article belongs to the Special Issue Microwave Photonics 2017)

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(a) Schematic diagram of the proposed dual-passband microwave photonic filter (with the courtesy of Dr. J. P. Yao). TLS(1,2): tunable laser source; PC(1–3): polarization controller; PM: phase modulator; EDFA(1,2): erbium-doped fiber amplifier; EPS-FBG: equivalent phase-shifted fiber Bragg grating; OC(1,2): optical circulator; DSF: dispersion-shifted fiber; PD: photodetector; VNA: vector network analyzer. (b) RF frequency response of the resultant dual-passband filter (with the courtesy of Dr. J. P. Yao)—the 1st passband is kept unchanged while the 2nd passband is tuned. Full article ">Figure 2
(a) Schematic diagram of the reconfigurable and tunable dual-band microwave photonic filter. BBS: broadband optical source; MZM: Mach-Zehnder modulator; PD: photodiode; PC(1,2): polarization controller; ODL: variable optical delay line. (b) Resultant dual-passband filter with two passbands (adapted from [<a href="#B31-photonics-04-00045" class="html-bibr">31</a>] with the courtesy of Dr. H. Fu). (c) Reconfigured microwave photonic filter with just one passband (with the courtesy of Dr. H. Fu). Full article ">Figure 3
Schematic diagram of the microwave photonic filter with independently tunable passbands (with the courtesy of Dr. Y. Jiang). BBS: broadband optical source, BPF: optical filter, ODL(1,2): optical delay line, VOA(1,2): variable optical attenuator, PM: phase modulator, DCF: dispersion compensating fiber, PD: photodetector. Full article ">Figure 4
(a) Experimental setup of the Lyot loop filter based frequency band selectable dual-band bandpass filter. BBS: broadband source; P1, P2: polarizers; C1, C2: circulators; PC: polarization controller; PMF: birefringent fiber; PM: phase modulator; DCF: dispersion compensating fiber; PD: photodetector; NA: network analyzer. (b) (i–iv) Multi-wavelength optical carriers with different comb spacings and combinations; (v–viii) Resultant frequency responses of the microwave photonic dual-band filter. Full article ">Figure 5
(a) Operation principle of the optically controlled Lyot loop filter. The pump laser and the SOA work as an optically controlled polarization controller through ultrafast nonlinear polarization rotation effect. (b) Tuning speed measurement of the optically controlled microwave photonic dual-band filter. The filter is switching between the all-block and single-band states. Full article ">Figure 6
(a) Experimental setup of the loop mirror (LMF) based three-passband microwave photonic filter. BBS: broadband light source; PMF: high-birefringent fiber; PM: phase modulator; SMF: standard single mode fiber; PD: photodetector. (b) Resultant filter response with reconfigurable passbands (with the courtesy of Dr. Y. Jiang): (i) one passband, (ii) two passbands, (iii) three passbands. Full article ">Figure 7
(a) Twelve possible combinations of the high-order Lyot loop filter based microwave photonic multiband filter (L1 = 11 m, L2 = 55 m). (b) Experimental setup of the reconfigurable microwave photonic multiband filter with twelve passbands based on a high-order Lyot loop filter [<a href="#B33-photonics-04-00045" class="html-bibr">33</a>]. BBS: broadband optical source; P1, P2: polarizers; PC1, PC2: polarization controllers; PMF1, PMF2: polarization maintaining fibers; PM: optical phase modulator; DCF: dispersion compensating fiber; PD: photodetector. Full article ">Figure 8
Measured frequency spectra of the reconfigurable microwave photonic multiband filter with different passband combinations [<a href="#B33-photonics-04-00045" class="html-bibr">33</a>]. (a) One single passband at 5.4 GHz. (b) Two passbands at 8.1 GHz and 16.2 GHz. (c) Three passbands at 6.7 GHz, 8.1 GHz and 13.6 GHz. (d) Five passbands at 5.4 GHz, 8.1 GHz, 12.2 GHz, 13.6 GHz, and 14.9 GHz. (e) Seven passbands from 1.3 GHz to 9.5 GHz. (f) Twelve passbands from 1.3 GHz to 16.2 GHz (All twelve passbands shown in <a href="#photonics-04-00045-f007" class="html-fig">Figure 7</a>a). Full article ">Figure 9
(a) Experimental setup of the SBS based multiband microwave phonic filter (courtesy of Dr. A. Choudhary). PM: phase modulator; CHIP: chalcogenide chip; PD: photodetector; AWG: arbitrary waveform generator. (b,c) Measured RF response with four and six passbands each separated by 250 MHz and 300 MHz, respectively (with the courtesy of Dr. A. Choudhary). Full article ">Figure 10
(a) Experimental setup of the cascaded tunable multiband microwave photonic filter [<a href="#B36-photonics-04-00045" class="html-bibr">36</a>]. SLD: Superluminescent diode; MZI: Mach-Zehnder interferometer; EOM: electro-optic modulator; DCF: dispersion compensating fiber; PD: photodetector. (b) 13 possible combinations of the cascaded MZI based microwave photonic multiband filter. Full article ">Figure 11
Measured frequency spectra of the tunable and reconfigurable microwave photonic multiband filter with different passband combinations [<a href="#B36-photonics-04-00045" class="html-bibr">36</a>]. (a) One single passband. (b–d) Three to five passbands. (e) Eight passbands. (f) Thirteen passbands with evenly distributed frequency spacing. (g) Eleven passbands. (h) Thirteen passbands with uneven frequency spacings. Full article ">Figure 12
Measured RF equalization functions obtained by the multiband filter based RF equalizer. Full article ">Figure 13
Demonstration of the pulse shaping function based on the proposed RF equalizer. (a) RF spectrum of a square-like pulse that to be reshaped. (b) Reshaped into a Gaussian pulse through the low-pass equalization function. (c) Reshaped into a triangular pulse trough the saw-tooth equalization function. Insets: Waveforms of the corresponding pulses in time domain. Full article ">

12019 KiB

Open AccessFeature PaperReview

Simultaneous Multi-Channel Microwave Photonic Signal Processing

by Lawrence R. Chen, Parisa Moslemi, Ming Ma and Rhys Adams

Photonics 2017, 4(4), 44; https://doi.org/10.3390/photonics4040044 - 17 Nov 2017

Cited by 5 | Viewed by 6343

Abstract

Microwave photonic (MWP) systems exploit the advantages of photonics, especially with regards to ultrabroad bandwidth and adaptability, features that are significantly more challenging to obtain in the electronic domain. Thus, MWP systems can be used to realize a number of microwave signal processing [...] Read more.

Microwave photonic (MWP) systems exploit the advantages of photonics, especially with regards to ultrabroad bandwidth and adaptability, features that are significantly more challenging to obtain in the electronic domain. Thus, MWP systems can be used to realize a number of microwave signal processing functions including, amongst others, waveform generation and radio-frequency spectrum analysis (RFSA). In this paper, we review recent results on fiber and integrated approaches for simultaneous generation of multiple chirped microwave waveforms as well as multi-channel RFSA of ultrahigh repetition optical rate pulse trains. Full article

(This article belongs to the Special Issue Microwave Photonics 2017)

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