Superluminescent Diode Research Articles

Live electrooptic imaging with a low-coherence optical LO signal source for suppression of interference noises.

Reported in this paper is the first application, to our knowledge, of a low-coherence optical local oscillator signal source to the live electrooptic imaging (LEI) scheme, where high frequency electric field (EF) distributions are visualized in real time. A fiber-optic super luminescent diode (SLD) in conjunction with a LiNbO3 Mach-Zehnder modulator (MZM) was found to work well for the real-time imaging of gigahertz-range EF distributions with high suppression of interference pattern image noises (IPINs), which have long been a problem to be solved. While the SLD-based LEI system works up to the MZM bandwidth (10GHz), IPINs caused by microscopic defects in an electrooptic sensor appear, suggesting a limitation given by the SLD coherence length.

Bonding stress and reliability of low-polarization quantum-well superluminescent diode

Mechanical stress induced by bonding low-polarization GaAsP/AlGaAs quantum-well superluminescent diodes with p-side-up and p-side-down bonding methods has been observed using measurements of the degree of polarization. Due to the closer distance from the heat-sink to active region and the thermal expansion coefficient mismatch between the oxygen-free copper heat-sink and GaAs-based chip, p-side-down bonding configuration were observed to have a larger stress than p-side-up one. The high temperature accelerated aging test of SLDs with both bonding methods was carried out and discussed. Results suggested that such a bonding stress in superluminescent diode might degrade device's performance, i.e. reducing the threshold level of catastrophic optical damage and improving the failure rate on accelerated aging test.

Concurrent illumination and communication: A survey on Visible Light Communication

The exceptional increase in the mobile data traffic leads to over exploitation of the radio frequency (RF) spectrum making it to become overcrowded. This necessitates relying on novel technology like Visible Light Communication (VLC) which utilizes cost-effective and solid-state illuminating devices like Light Emitting Diodes (LEDs). The stunning notability of enabling contemporaneous illumination and communication has driven VLC to become a revolutionary alternative to RF. This survey provides an elaborate analysis of the VLC system model, optical channel environment, modulation techniques, detailed analysis on different variants of optical orthogonal frequency division multiplexing (OOFDM), and other modulation formats like carrier-less amplitude and phase modulation (CAP) and multi-band CAP (m-CAP) which bestows with the most feasible solution for VLC in the perspective of spectral, power and computational efficiency. In addition, multiple access schemes like orthogonal frequency division multiple access (OFDMA), non orthogonal multiple access (NOMA) is also the focus of this survey. Furthermore, the research advancements in enabling organic LEDs (OLEDs) and superluminescent diodes (SLDs) to penetrate the solid state lighting (SSL) industry is also highlighted. This survey provides insights about the programmable test beds facilitating real time application and signifies how VLC can be amalgamated with both the lighting infrastructure and intelligent transportation system (ITS) in smart cities. In addition, certain research challenges to be addressed is also the part of this survey.

A tutorial on laser-based lighting and visible light communications: device and technology [Invited

This tutorial focuses on devices and technologies that are part of laser-based visible light communication (VLC) systems. Laser-based VLC systems have advantages over their light-emitting-diode-based counterparts, including having high transmission speed and long transmission distance. We summarize terminologies related to laser-based solid-state lighting and VLC, and further review the advances in device design and performance. The high-speed modulation characteristics of laser diodes and superluminescent diodes and the on-chip integration of optoelectronic components in the visible color regime, such as the high-speed integrated photodetector, are introduced. The modulation technology for laser-based white light communication systems and the challenges for future development are then discussed.

Zastosowanie terapii fotodynamicznej z użyciem pulsacyjnej superluminescencyjnej lampy sLED w rogowaceniu słonecznym

Zastosowanie terapii fotodynamicznej z użyciem pulsacyjnej superluminescencyjnej lampy sLED w rogowaceniu słonecznym

Development of a Broadband Superluminescent Diode Based on Self-Assembled Quantum Dots for Optical Coherence Tomography Applications

Development of a Broadband Superluminescent Diode Based on Self-Assembled Quantum Dots for Optical Coherence Tomography Applications

3D Information Retrieving of Concealing Surface beneath Opaque Resin Layer by Fast-Fourier Low Coherence Interferometer

A normalized contrast method on a Superluminescent diode (SLD) low coherence interferometer could retrieve 2D image concealing under a light-scattering medium. In addition, a continuous wavelet transform on both white light and SLD vertical scanning interferometry could construct 3D profile of the interfaces in a dual-layer structure. In this research, 3D information on surface, concealing beneath opaque resin layer, will be produced by using SLD phase difference interferometry with a Fast Fourier Transform. The effect of opaqueness of coating resin layer to quality of 3D image from our method will be revealed.

Effects of Modulation P-Doping on Thermal Stability of InAs/GaAs Quantum Dot Superluminescent Diodes

Effects of Modulation P-Doping on Thermal Stability of InAs/GaAs Quantum Dot Superluminescent Diodes

High performance continuous-wave InP-based 2.1 μm superluminescent diode with InGaAsSb quantum well and cavity structure suppression

Broadband spectrum electrically pumped InP-based superluminescent diodes with high output power in continuous-wave (CW) mode are reported. The optimized active region and high quality of quantum wells are guaranteed for controlling the wavelength and acquiring large mode gain. Three kinds of cavity structures were designed to provide strong suppression of reflections allowing strong amplified spontaneous emission without any sign of lasing modes. All device spectrums are centered around 2.1 μm, and at low injection current, the full width at half maximum (FWHM) of the widest spectrum is 99 nm. After the optimization of the waveguide structure for higher output power, the maximum CW output power is lifted up to 30 mW with the two lobe far field pattern in a single output facet at 300 K and still the FWHM of 41 nm. This work is of great importance to pave the way for demonstrating compact and efficient light sources based on InP material systems. Considering the InP material compatibility with the mature device fabrication process, especially the buried heterostructure, device characteristics would be better improved and be more promising for applications.

High-power blue superluminescent diode for high CRI lighting and high-speed visible light communication.

We demonstrated a high-power (474 mW) blue superluminescent diode (SLD) on c-plane GaN-substrate for speckle-free solid-state lighting (SSL), and high-speed visible light communication (VLC) link. The device, emitting at 442 nm, showed a large spectral bandwidth of 6.5 nm at an optical power of 105 mW. By integrating a YAG-phosphor-plate to the SLD, a CRI of 85.1 and CCT of 3392 K were measured, thus suitable for solid-state lighting. The SLD shows a relatively large 3-dB modulation bandwidth of >400 MHz, while a record high data rate of 1.45 Gigabit-per-second (Gbps) link has been achieved below forward-error correction (FEC) limit under non-return-to-zero on-off keying (NRZ-OOK) modulation scheme. Our results suggest that SLD is a promising alternative for simultaneous speckle-free white lighting and Gbps data communication dual functionalities.

InPBi Quantum Dots for Super-Luminescence Diodes.

InPBi thin film has shown ultra-broad room temperature photoluminescence, which is promising for applications in super-luminescent diodes (SLDs) but met problems with low light emission efficiency. In this paper, InPBi quantum dot (QD) is proposed to serve as the active material for future InPBi SLDs. The quantum confinement for carriers and reduced spatial size of QD structure can improve light emission efficiently. We employ finite element method to simulate strain distribution inside QDs and use the result as input for calculating electronic properties. We systematically investigate different transitions involving carriers on the band edges and the deep levels as a function of Bi composition and InPBi QD geometry embedded in InAlAs lattice matched to InP. A flat QD shape with a moderate Bi content of a few percent over 3.2% would provide the optimal performance of SLDs with a bright and wide spectrum at a short center wavelength, promising for future optical coherence tomography applications.

(Invited) Fine Temperature Monitoring of Si Wafer for Plasma Processing

One of the critical parameters in many semiconductor-processing steps such as plasma etching, chemical vapor deposition, and so on, is the substrate temperature. For example, the etch rate and etch profile are sensitive to the substrate temperature in the plasma etching process. However, contact measurement such as thermo-couples and fluorescent temperature sensor cannot measure the accurate temperature, especially in low pressure due to poor thermal transfer between the wafer and the probe. We have developed the non-contact temperature measurement of substrates by using optical low-coherence interferometer. [1-6] The low-coherence interferometry is based on Michelson interferometry, and a white light such as a super-luminescent diode (SLD) was used as a low-coherence light source. SLD has the central wavelengths of 1325 nm and the full width at half maximum of 64.5 nm. The light which is reflected at the surface of Si substrate interfered with the light reflected at the scanning reference mirror. The interfered light was detected with a spectrometer and the signal which is a frequency domain spectrum was converted to a time domain signal by inverse Fourier transformation. The temperature of the Si substrate is derived from the change in the optical path length of Si substrate due to thermal expansion and changes in the refractive index. The temperatures of Si wafer and chamber parts made of Si were successfully monitored in the SiO2 plasma etching using capacitively coupled plasma. The performance was compared with that of fluorescent temperature sensor. From these results, we have demonstrated highly precise and rapid response measurement of the temperature of Si wafer at real time by using Fourier domain low coherence interferometer.

Characterization of an amplified piezoelectric actuator for multiple-reference optical coherence tomography.

The characterization of an amplified piezoelectric actuator (APA) as a new axial scanning method for multiple-reference optical coherence tomography (MR-OCT) is described. MR-OCT is a compact optical imaging device based on a recirculating reference-arm-scanning optical delay using a partial mirror that can enhance the imaging depth range by more than 10 times the reference mirror's scanning amplitude. The scanning amplitude of the used APA was varied between 30μm and 250μm, depending on the scanning frequency of between 0.8kHz and 1.2kHz. A silver-coated miniature mirror was attached to the APA via ultraviolet-cured optical adhesive, and the light source was a super-luminescent diode with 1310nm center wavelength and 56nm bandwidth. The sensitivity was measured with and without the partial mirror in the reference delay line as a function of scan speed, frequency, and range, therefore providing results for MR-OCT and TD-OCT modes. It was found that the APA provides more than twice the mechanical scanning range compared to other opto-mechanic actuators, but results indicate degradation of signal-to-noise ratio and sensitivity at larger imaging depths. In conjunction with MR-OCT, the scan range of maximum 200μm can be enhanced up to 1-1.5mm by using a reduced amount of orders of reflections, which could be of interest to increase sensitivity in the future.

Modeling and Simulation of the Intrinsic Function of a Photonic Switch

In this paper, I provide modeling and simulation results which show that a photonic bistable switch can be realized by the application of two superluminescent light emitting diodes to a configuration of three 10μm radius micro-ring resonators. The 130nm silicon on insulator rib structure is adopted for the simulations. The three 10μm radius rings have a resonant wavelength of 1.5487μm. The on or off state, at a single output port, is realized by the application of a superluminescent diode at either, one or the other, of the two input ports. The bistable output intensity, at the ring resonant wavelength, is shown as a single normalized peak representing a 1 or the “on” condition. The single peak is realized by the application of the “on” superluminescent diode. The “off” or the 0 condition, realized by the application of the “off” superluminescent diode, is exhibited at the output by the introduction of an optical transparency at the single peak resonant wavelength. The minimum of the optical transparency can be adjusted by changing the coupling gap distances of the design. The transparency mimum introduces an error detection feature whereby a failure of the “off” excitation superluminecent diode results in a zero or noise floor output. The transparency minimum can be increased to raise the off state minimum above the measurement apparatus noise floor. The output of the switch can be detected using a simple photodiode intensity detection method.

High-performance GaAs-based superluminescent diode with 292-nm emission bandwidth using simple dot-in-a-well structures

We report a simultaneous amplified emission from InAs-based self-assembled quantum dot and quantum well in a multistack dot-in-a-well superluminescent light-emitting diode (SLD) for application in broadband sources. A combination of atomic force microscopy, photoluminescence of the test structures, and optoelectronic characterization of SLD is used to obtain an emission bandwidth of ∼292 nm covering O–S communication band (including 850-nm band) and a maximum continuous power of ∼1.33 mW at room temperature.

Photodynamic therapy with the use of superluminescent diodes (sLED) in the treatment of actinic keratosis.

Superluminescent diodes (sLED) appear to be an innovative and promising light source in photodynamic therapy (PDT), especially in actinic keratosis (AK) lesions treatment. Assessment of tolerability and efficacy of sLED in topical 5-aminolevulinic acid (ALA) PDT of AK lesions. 27 patients received ALA PDT with the use of sLED with "soft starter". Tolerability of sLED lamp depended on the treated lesions field (extension) rather than on their thickness. In contrast sLED lamp efficacy depended on AK lesions thickness. sLED PDT is highly effective in the treatment of grade I and II AK lesions. Grade III AK lesions require further treatment.

Structural design and fabrication of 830 nm GaAsP/AlGaAs low polarization superluminescent diode with tensile-strained wells

In this paper, super luminescent diode (SLD) at 830 nm with high power efficiency and low polarization was reported. The mode gain of tensile-strained GaAsP/AlGaAs double-quantum well (DQW) was calculated by the Luttinger–Kohn Hamiltonian, including confinement effects and tetragonal strain. The results showed that the transverse-electric polarized mode gain was almost the same with transverse-magnetic polarized mode gain of the device with GaAs0.92P0.08 quantum well. Tensile-strained GaAs0.92P0.08/Al0.25Ga0.75As DQW SLD was prepared by Metal–organic Chemical Vapor Deposition. The SLD of ridge wave guide structure was fabricated with “J-shape” absorbing region structure with a tilt angle of 7°. The stack layers of TiO2 and SiO2 were coated on two facets as anti-reflection films, with residual facet reflectivity less than 1%. The SLD testing result showed the degree of polarization was 4%, optical power was 11.2 mW and peak wavelength of 824 nm at injection current was 100 mA. The experimental results were in good agreement with theoretical calculation results.

Image-guided Removal of Interproximal Lesions with a CO2 Laser.

Recent studies have shown that near-IR (NIR) imaging methods such as NIR reflectance can be used to image lesions on proximal surfaces, and optical coherence tomography (OCT) can be used to measure the depth of those lesions below the tooth surface. These imaging modalities can be used to acquire high contrast images of demineralized tooth surfaces, and 2-D and 3-D images can be extracted from this data. At NIR wavelengths longer than 1200-nm, there is no interference from stains and the contrast is only due to the increased light scattering of the demineralization. Previous studies have shown that image-guided laser ablation can be used to remove occlusal lesions, but its use for the removal of subsurface lesions on proximal surfaces has not been investigated. The objective of this study is to demonstrate that simultaneously scanned NIR and CO2 lasers can be used to selectively remove natural and artificial interproximal caries lesions with minimal damage to sound tooth structure. In this study, images of simulated and natural interproximal lesions on extracted teeth were imaged using a digital microscope, a scanned 1460-nm superluminescent laser diode with an InGaAs detector and a cross polarization OCT system operating at 1300-nm. The lesions were subsequently removed with a CO2 laser operating at 9.3-µm and the dental handpiece and the volume of sound tissue removed was compared.

Ghost Spectroscopy with Classical Thermal Light Emitted by a Superluminescent Diode

Ghost modalities are by no means ``spooky actions'', but are metrology schemes exploiting intensity correlations of light, based on the fundamentals of quantum optics. The authors demonstrate ghost spectroscopy based on classical photon correlations in the wavelength domain of broad-band light emitted by an ultraminiaturized superluminescent semiconductor diode. Comprehensive proof of principle is provided by a real-world experiment on chloroform at 1214 nm. This demonstrated analogy between ghost imaging and ghost spectroscopy is expected to further fertilize the field, to promote a deeper understanding, and to lead even to other protocols in ghost metrology.

GaSb superluminescent diodes with broadband emission at 2.55 μm

We report the development of superluminescent diodes (SLDs) emitting mW-level output power in a broad spectrum centered at a wavelength of 2.55 μm. The emitting structure consists of two compressively strained GaInAsSb/GaSb-quantum wells placed within a lattice-matched AlGaAsSb waveguide. An average output power of more than 3 mW and a peak power of 38 mW are demonstrated at room temperature under pulsed operation. A cavity suppression element is used to prevent lasing at high current injection allowing emission in a broad spectrum with a full width at half maximum (FWHM) of 124 nm. The measured far-field of the SLD confirms a good beam quality at different currents. These devices open further development possibilities in the field of spectroscopy, enabling, for example, detection of complex molecules and mixtures of gases that manifest a complex absorption spectrum over a broad spectral range.