Lightwave Modulation Research Articles

Snapshot depth–spectral imaging based on image mapping and light field

Depth–spectral imaging (DSI) is an emerging technology which can obtain and reconstruct the spatial, spectral and depth information of a scene simultaneously. Conventionally, DSI system usually relies on scanning process, multi-sensors or compressed sensing framework to modulate and acquire the entire information. This paper proposes a novel snapshot DSI architecture based on image mapping and light field framework by using a single format detector. Specifically, we acquire the depth – spectral information in two steps. Firstly, an image mapper is utilized to slice and reflect the first image to different directions which is a spatial modulation processing. The modulated light wave is then dispersed by a direct vision prism. After re-collection, the sliced dispersed light wave is recorded by a light field sensor. Complimentary, we also propose a reconstruction strategy to recover the spatial depth – spectral hypercube effectively. We establish a mathematical model to describe the light wave distribution on every optical facet. Through simulations, we generate the aliasing raw spectral light field data. Under the reconstruction strategy, we design an algorithm to recover the hypercube accurately. Also, we make an analysis about the spatial and spectral resolution of the reconstructed data, the evaluation results conform the expectation.

Electrical tunable topological valley photonic crystals for on-chip optical communications in the telecom band

Abstract On-chip optical communications are in increasingly demand for low-loss, small-footprint and power-efficient waveguiding solutions in the telecom band. However, most integrated optical circuits suffer from high propagation loss and low integration degree. Through manipulating the valley-dependent topological phase of light, we have experimentally demonstrated both robust optical transport and electrical modulation of lightwaves at telecom wavelengths in the valley photonic crystals. With the adoption of valley kink states, the 25 Gbit/s optical signal at 1550 nm is successfully transmitted through a highly twisted interface. Furthermore, an extreme high data rate of 100 Gbit/s is demonstrated with such topological waveguide by wavelength division multiplexing. The electrical tunability of the topological modulators based on thermo-optic effect is also verified, opening a novel route towards active valley kink photonic devices. Our study shows a great possibility of making use of the topological protection in building up high-speed datalinks on a chip.

Kerr nonlinear medium assisted double-face absorbers for differential manipulation via an all-optical operation.

Recently, light absorbers have attracted great attentions due to their promising in applications in functional optoelectronic devices. Herein, we theoretically propose and numerically demonstrate a new absorber platform, which consists of a 280-nm-thick photonic nonlinear waveguide film covering on the metal grating structure. Strong reflection inhibition and absorption enhancement is achieved in both the forward and backward directions, which indicates potential novel performances since the previous reports only achieved absorption in one side due to the using of opaque metal film substrate or the reflective mirror. The anti-reflection bands or the absorption peaks at the shorter and longer wavelength ranges are related to the excitation of the propagating surface plasmon resonance by the slit-assisted grating and the cavity mode by the slit in the metal film. Strong differential manipulation is realized for the double-face absorbers via the all-optical operation. Moreover, the operation wavelengths for the double-face light absorber can be modified strongly via using an asymmetric dielectric medium for the coating films. These new findings pave approaches for subtractive lightwave modulation technology, selective filtering, multiplex sensing and detection, etc.

Broad-spectrum diffractive network via ensemble learning

We propose a broad-spectrum diffractive deep neural network (BS-D2NN) framework, which incorporates multiwavelength channels of input lightfields and performs a parallel phase-only modulation using a layered passive mask architecture. A complementary multichannel base learner cluster is formed in a homogeneous ensemble framework based on the diffractive dispersion during lightwave modulation. In addition, both the optical sum operation and the hybrid (optical-electronic) maxout operation are performed for motivating the BS-D2NN to learn and construct a mapping between input lightfields and truth labels under heterochromatic ambient lighting. The BS-D2NN can be trained using deep learning algorithms to perform a kind of wavelength-insensitive high-accuracy object classification.

Coupled InGaAs Quantum Dots for Electro-Optic Modulation

We investigated the growth of vertically coupled In0.75Ga0.25As quantum dots (QDs) by varying the GaAs spacer thickness (d). Vertically-aligned triple-layer QDs of uniform size and highest accumulated strain are formed with d = 5 nm. The electroluminescence (EL) characteristics for In0.75Ga0.25As QDs show an emission spectrum at optical wavelength (λ) of 1100−1300 nm. The EL spectra exhibit the highest optical gain at λ ~ 1200 nm, and the narrowest FWHM = 151 nm of the sample with d = 5 nm at injection current = 20 mA. Fabry–Perot measurements at λ = 1515 nm of TE and TM polarizations were carried out to investigate the electro-optic modulation for a single-mode ridge waveguide consisting of vertically-coupled triple-layer In0.75Ga0.25As QDs (d = 5 nm). The linear (r) and quadratic (s) electro-optic coefficients are r = 2.99 × 10−11 m/V and s = 4.10 × 10−17 m2/V2 for TE polarization, and r = 1.37 × 10−11 m/V and s = 3.2 × 10−17 m2/V2 for TM polarization, respectively. The results highlight the potential of TE/TM lightwave modulation by InGaAs QDs at photon energy below energy band resonance.

21‐2: Invited Paper: 1µm Pixel Pitch Spatial Light Modulator Panel for Digital Holography

Digital hologram images reconstructed through interference of the modulated light waves requires ultra high resolution display panel. BCE oxide TFTs with channel width of 0.5µm and channel length of 2µm were stacked on data line for the integration of 1µm pitch pixel. 1µm pixel pitch 16K spatial light modulator on glass substrate was successfully fabricated with vertically stacked TFT structure.

Novel RF-source-free reconfigurable microwave photonic radar.

A novel reconfigurable microwave photonic (MWP) radar has been proposed and experimentally demonstrated. At a transmitting end, a microwave signal with a large bandwidth and ultra-low phase noise is generated by a Fourier domain mode locking optoelectronic oscillator. At a receiving end, photonics-based de-chirp processing is implemented by phase-modulating light waves in a dual-drive Mach-Zehnder modulator and mixing the modulated light waves at a photodetector. Without the requirement of external RF sources, the developed photonics-assisted programmable radar is capable of generating and processing microwave signals with adjustable format, bandwidth and central frequency. The proposed radar working from X to Ku band with an instantaneous bandwidth of 2 GHz is demonstrated. The reconfiguration of the radar is theoretically analyzed. The tunability of radar bandwidth and central frequency is investigated. Microwave imaging of a pair of trihedral corner reflectors based on the developed MWP radar is achieved.

Vector Modulation by Laser and Electroabsorption Modulator With Digital Pre-Coding and Pre-Compensation

We present a method to achieve vector modulation of lightwave using an electroabsorption modulator intregrated laser. The laser section is used for direct phase modulation followed by an amplitude modulation of the electroabsorption modulator section in a cascade manner, which is an alternative method to conventional IQ modulator. To allow an improved phase demodulation, we propose a digital pre-compensation technique for a transmitter in optical coherent system for the first time, which includes a phase-balanced differential phase shift keying encoding and a digital domain pre-equalization filtering. The phase-balanced encoding technique applies parallel DC-balance coding with a phase-balanced symbol mapping, which results in a bounded cumulative phase and a constant statistical characteristic of the modulating signal in differential M-ary phase shift keying and M-ary quadrature amplitude modulation formats. The digital pre-equalization filter also compensates for the phase response of the laser section. Experimental results show that the pre-digital compensation technique allows the improved complex signal demodulation compared to conventional DQPSK modulation in a back-to-back setup.

Pendekatan Saintific Quantum dalam Memahami Perjalanan Isra’ Nabi Muhammad SAW (Teori Saintifik Modulasi Quantum Isra’)

Abstract
 This paper examined the journey of Isra Prophet Muhammad SAW with the Quantum Scientific Approach. In this paper, the theory of Isra’s Quantum scientific modulation is used with deep discussion through theoretical, empirical, scientific and modulation also quantum verification. The result of this paper explained that Isra 'Mi'raj was the event of Prophet Muhammad's execution in the evening which was aimed to pick up the five-hour prayer commands consisting of 17 Raka’ats according to the letter of Al-Isra [17] verse 1. This event examined our faith in God because if we use logically thinking without faith it is difficult to make a sense, furthermore, it is as wisdom for man that God, in giving orders is using the laws of cause and effect (sunatullah). Therefore, the journey of Isra' performed by Prophet Muhammad SAW was accompanied by Gabriel with Buraq. Theoretically, this journey was supported by the quantum theory of light, Einstein's relativity, light wave modulation and the theory of annihilation and teleportation theory. These theories reinforce the power of Allah SWT in giving the command to his prophets is always in accordance with the nature of his irodat that prevailed in the universe. In accordance with the approach and material review with the scientific verification of the quantum, this theory is called the Isra’ Quantum Modulation Theory. Although, in empirically it can be proved, but this journey remains a secret of God that cannot be solved by reason and human science, because the experiment it’s only done on electrons and protons that are very small and lifeless, whereas inanimate objects and humans it has not been able to prove, so the journey of Isra and Mi'raj of the Prophet Muhammad remains us a miracle that cannot be obtained by others.
 
 Keywords: Scientific, Quantum, Isra', Modulation

Proposed high-speed micron-scale spatial light valve based on a silicon-graphene hybrid structure.

We propose a new ultracompact CMOS-compatible variable-transmission spatial light valve based on a silicon-graphene hybrid structure. Normally incident ∼1560 nm light can be coupled to a silicon-graphene-based 1D photonic crystal cavity through a perturbation-based diffractive coupling scheme. The lightwave modulation is achieved by tuning the Fermi level of the graphene, which can change both the loss and the resonant wavelength of the cavity. Based on finite-difference time-domain simulation, the modulation depth is larger than 10 dB with driving voltage of about 4.8 V(pp) while the modulation speed is estimated to be higher than 45 GHz.

Quadruple-wavelength THz modulator based on compound lattice PC with direct-coupled and side-coupled structure

As a key device of THz technologies, the THz modulator based on PC can realise the modulation of light waves. However, the traditional tunable PC modulator can only achieve a single beam of THz wave modulation by controlling a point defect, and multi-wavelength modulation can be realised by controlling the corresponding number of point defects with a complex operation. With the rapid development of microwave and light wave communication technology, the quadruple-wavelength THz modulator based on compound lattice PC can realise the 'on' and 'off' modulation of THz waves in quadruple-wavelength through the controlling of only two defects, using direct-coupled structure and side-coupled structure, respectively. We analyse and compare the performance of the quadruple-wavelength THz modulator based on compound lattice PC with the two kinds of structures. The results show that the contrast ratio is 44.6 dB and 13.8 dB, insert loss is 0.43 dB and 0.18 dB, and modulation rate is 7.1 GHz and 8.6 GHz of the modulator with direct-coupled structure and side-coupled structure, respectively. The modulator with direct-coupled structure has a higher contrast ratio, and can achieve modulation quadruple-wavelength of THz wave when the distance between the point defects is very short. The modulator with side-coupled structure is more excellent in the performance of insert loss and modulation rate.

Broadband 60 GHz Sounder for Propagation Channel Measurements Over Short/Medium Distances

This paper presents a millimeter-wave propagation-channel sounder that uses an optical-fiber cable to achieve phase coherence between transmitting and receiving antennas using two modulated light waves in the vicinity of 1550 nm. In the described sounder, the optical-fiber cable approach permits a separation of up to almost 1000 m between the transmitter and receiver because of the low level of attenuation per unit length in a single-mode optical-fiber cable. The measurement system can sweep from 500 MHz below 60.1 GHz (59.6 GHz) to 500 MHz above 60.1 GHz (60.6 GHz) and proceed to 10 001 in-phase and in-quadrature propagation channel measurements in ${\sim}{\rm 5}~{\rm sec.}$ Measurements of the frequency response of nonline-of-sight and line-of-sight indoor/outdoor propagation channels over medium $({>}{\rm 100}~{\rm m})$ and short ranges can be performed for two or more different lateral receiving antenna positions for antenna diversity studies.

Modulated light wave tumor therapy [MLW]: case study

MLW was developed as the GP Einstein optical system as an alternative to conventional approaches to tumor therapy where such conventional therapies may not be indicated. By application of MLW we were able to shrink an abdominal tumor mass from 37 mm to 5 mm without chemotherapy or invasive surgical treatment. A controlled dose of modulated light irradiation, resulting in a change of the physiologic properties of the targeted tissue and bring their characteristic frequencies to the levels characteristic of corresponding healthy tissues. In MLW the Electromagnetic wave emitted by a modulated light wave and absorbed by a human tissue may serve as a “messenger” so that pathologic changes may be corrected by natural tissue repair mechanisms. With individualization of MLW frequencies, the condition and degree of pathology and the time‐dependent properties of MLW it may be able to treat a wide range of abdominal tumors. Institutional Support

Discrimination of wireless electromagnetic signals by electro-optic modulators using an array of patch antennas embedded with orthogonal gaps

We proposed a new wireless electromagnetic signal discrimination device using electro-optic modulators and an array of planar patch antennas embedded with orthogonal gaps. Wireless electromagnetic signals can be detected and converted directly to lightwave signals through optical modulation. The magnitude, phase, and polarization of the wireless signal can be measured precisely and identified. By using meandering gap structures, the directivity of the wireless signal conversion can be tuned more precisely. Furthermore, the directivity of the wireless signal conversion in two-dimensional space can also be obtained by comparing two orthogonal modulated lightwave signals from two orthogonal optical waveguides. The design and analysis of the device and experiments at an operational frequency of 26 GHz are presented.

Peacock feather supported self assembled ZnO nanostructures for tuning photonic properties

Barbules of the peacock feather have been used as the natural template for developing assemblies of zinc oxide (ZnO) nanospheres. The different colored barbules consisting of various photonic crystals (extracted from eye-pattern) were characterized in terms of the stop-bands identified in the respective Reflectance spectra. The stop-bands of the photonic crystals are found to get red-shifted after the loading of ZnO nanospheres and was reasoned to the modification of photonic band gap. The ZnO nanosphere decorated barbules show well defined photoluminescence response with dominant defect related emission of ZnO. The artificially grown inorganic structures on natural templates form a basis of new hybrid system that can help in exploiting photonic band gap engineering and light wave modulation with high selectivity.

Molecular-Modulated Mode-Locked Laser to Generate a Continuous-Wave Pulse Train with an Ultrahigh Repetition Rate

We propose a novel approach to generate a continuous-wave pulse train with an ultrahigh repetition rate. The method utilizes a unique mechanism of lightwave modulation and amplification based on a continuous-wave Raman interaction in a high-finesse optical cavity. We experimentally demonstrated the generation of multifrequency emissions from a hydrogen-filled cavity and measured the intensity-modulated waveform at the frequency of 17.6THz. We found that the intracavity dispersion caused phase mismatch between the related longitudinal modes; thus preventing the phase-locked generation of a continuous-wave-based THz pulse train. This undesirable behavior can be overcome by using a dispersion-managed and bandwidth-extended cavity; this will then lead to a new-type of mode-locked laser operating at a frequency of more than 10THz.

Nonlinear phase shifts of modulated light waves with slow and superluminal group delay in stimulated Brillouin scattering

Brillouin amplification with counterpropagating modulated pump and Stokes light leads to nonlinear modulation-phase shifts of the interacting intensity waves. This is due to a partial transformation of the nonmodulated light component at the input into modulated light at the output as a result of a mixing process with the counterpropagating modulated component of the pump and results in an advance or delay of the input modulation. This occurs for interactions over less than half of a modulation wavelength. Milliwatts of power in a kilometer of standard single-mode fiber give significant tunability of the modulation phase.

Demodulation Pixel Based on Static Drift Fields

A novel pixel architecture for two-dimensional pixel parallel demodulation of modulated light waves is introduced, enabling real-time three-dimensional (3-D) imaging. Applications for such methods can be found in the field of surveillance, robotics, automotive, and industry security applications. The pixel architecture is based on large areas of static drift fields and relatively small demodulation regions. The large area of static drift field forms the basic photodetection region. The constant drift field enables the very fast transport of photo-generated charges to the sampling region where demodulation of the light signal is performed. The main advantages compared to recently used demodulation pixels are lower power consumption and higher optical fill factor or sensitivity. The first implementation is a pixel of 40times40 mum <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> size with 25% optical fill factor. Measurements prove the concept of transporting photo-generated charges within less than 1 ns to the demodulation node. The applicability of the pixel in 3-D imaging applications is highlighted by distance measurements achieving millimeter distance resolution

Lithium niobate optical modulators: Devices and applications

Optical modulators, using acousto-optic, magneto-optic or electro-optic effects, as the principal components for external modulation of lightwaves, have presently played the important role in modern long-haul ultra-high speed optical communications and photonic signal processing systems. LiNbO 3 is an ideal host material for such modulators. In this paper we present: (i) a brief overview the electro-optic interaction in LiNbO 3 optical waveguides and the travelling electric waves for modulation; (ii) fabrication techniques of optical waveguides and electrodes for the excitation of microwave and millimeter waves, including the prospects of the uses of ultra-thick “brick-wall like” type by synchrotron deep X-ray LIGA process; (iii) a comprehensive modelling of the travelling wave electrodes for the design of interferometric optical modulators, including different electrode structures. Tilted and thick and “brick-wall” like electro-plated electrodes are modelled and confirmed with implemented modulators operating up to 26 GHz in diffused LiNbO 3 optical interferometric waveguide structures; (iv) the design and implementation of LiNbO 3 single or dual drive as modulators for modulating lightwaves in modern transmission systems as ultra-high speed pulse carvers, generators of modulation formats (NRZ, RZ, CS-RZ, DPSK, DQPSK, etc.) and photonic signal processors.

Continuous true-time-delay beamforming employing a tunable multiwavelength fiber ring laser source with equally increased or decreased wavelength spacing

The authors propose a true-time-delay system for wideband continuous phased array beamforming using a chirped grating-based true-time-delay beamforming network incorporating a novel multiwavelength tunable fiber ring laser with equally increased or decreased wavelength spacing. The wavelength of each lasing is determined by the fiber Bragg grating in the laser cavity and tuned by compressing or stretching the fiber Bragg grating. For simultaneously achieving N tunable lasings, N fiber Bragg gratings are used. To ensure wavelength tuning with equally increased or decreased wavelength spacing, the N fiber Bragg gratings are mounted on an organic plastic plate with angles between adjacent gratings such that the tuning forces applied to the gratings experience equal increments. Time delays with equally increased or decreased time-delay difference for the equally spaced wavelengths are obtained when the modulated light waves are reflected at different locations of a linearly chirped grating. A four-channel chirped-grating-based true-time-delay system using the proposed light source for continuous beamsteering at microwave frequencies up to 10 GHz has been constructed and demonstrated.