Light source with orthogonally linear polarized two‐frequency beam from laser diode and surface profile measurement

The identification of food products and the detection of adulteration are of global interest for food safety and quality control. We present a non-invasive in-situ approach for the differentiation of meat from selected animal species using microsystem diode laser based shifted excitation Raman difference spectroscopy (SERDS) at 671 nm and 785 nm. In that way, the fingerprint Raman spectra can be used for identification without a disturbing fluorescence background masking Raman signals often occurring in the investigation of biological samples. Two miniaturized SERDS measurement heads including the diode laser and all optical elements are fiber-optically coupled to compact laboratory spectrometers. To realize two slightly shifted excitation wavelengths necessary for SERDS the 671 nm laser (spectral shift: 0.7 nm, optical power: 50 mW) comprises two separate laser cavities each with a volume Bragg grating for frequency selection whereas the 785 nm light source (spectral shift: 0.5 nm, optical power: 110 mW) is a distributed feedback laser. For our investigations we chose the most consumed meat types in the US and Europe, i.e. chicken and turkey as white meat as well as pork and beef as red meat species. The applied optical powers were sufficient to detect meat Raman spectra with integration times of 10 seconds pointing out the ability for a rapid discrimination of meat samples. Principal components analysis was applied to the SERDS spectra to reveal spectral differences between the animals suitable for their identification. The results will be discussed with respect to specific characteristics of the analyzed meat species.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

A technique for measuring surface roughness in the submi- crometer range is developed. The principle of the method is based on laser scattering from a rough surface. A telecentric optical setup that uses a laser diode as a light source is used to record the light field scattered from the surface of a rough object. The light intensity distribu- tion of the scattered band, which is correlated to the surface roughness, is recorded by a linear photodiode array and analyzed using a single- chip microcomputer. Several sets of test surfaces prepared by different machining processes are measured and a method for the evaluation of surface roughness is proposed. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)00406-2)

Unwanted hair growth remains a therapeutic challenge and there is a considerable need for an effective and safe treatment modality. From an evidence-based view to summarize efficacy and adverse effects from hair removal with ruby, alexandrite, diode, and Nd:YAG lasers and intense pulsed light (IPL). Original publications of controlled clinical trials were identified in Medline and the Cochrane Library. A total of 9 randomized controlled (RCTs) and 21 controlled trials (CTs) were identified. The best available evidence was found for the alexandrite (three RCTs, eight CTs) and diode (three RCTs, four CTs) lasers, followed by the ruby (two RCTs, six CTs) and Nd:YAG (two RCTs, four CTs) lasers, whereas limited evidence was available for IPL sources (one RCT, one CT). Based on the present best available evidence we conclude that (i) epilation with lasers and light sources induces a partial short-term hair reduction up to 6 months postoperatively, (ii) efficacy is improved when repeated treatments are given, (iii) efficacy is superior to conventional treatments (shaving, wax epilation, electrolysis), (iv) evidence exists for a partial long-term hair removal efficacy beyond 6 months postoperatively after repetitive treatments with alexandrite and diode lasers and probably after treatment with ruby and Nd:YAG lasers, whereas evidence is lacking for long-term hair removal after IPL treatment, (v) today there is no evidence for a complete and persistent hair removal efficacy, (vi) the occurrence of postoperative side-effects is reported low for all the laser systems. The evidence from controlled clinical trials favours the use of lasers and light sources for removal of unwanted hair. We recommend that patients are pre-operatively informed of the expected treatment outcome.

We develop a laser-diode phase-shifting interferometer that can capture frame-rate phase-shifted interferograms on a video tape with a high capacity for their storage. The number of the video frame is simultaneously recorded on an audio track of the video tape. In a four- step manner, the injection-current variation of the laser diode is synchro- nized with the field pulse of a CCD camera to producep/2-step phase shifts at a frame rate of 1/30 s. An intensity distribution of the interfero- gram on any frame can be determined through a video tape with a frame memory using the recorded frame number. The four successive phase- shifted interferograms are used to calculate a distribution of frozen phase by a phase-extraction algorithm. The phase error due to the frame-by- frame intensity repeatability is theoretically analyzed. © 1999 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(99)01812-7)

BackgroundBurn injuries and surgical drape fires are known potential complications of endoscopic surgery. Automatic standby technology (AST) triggers the light source to immediately enter "standby mode" when the light cable disconnects from the endoscope, which should reduce the likelihood of patient and caregiver injuries and operating room drape fires.ObjectiveThis study compared AST versus a conventional light source without this technology, examining temperature differences at the endoscope tip and adapter, as well as the propensity of disconnected light cables to burn surgical drapes.MethodsAST and conventional light sources with standard light cables were connected to 4 mm rigid nasal endoscopes. Temperature was measured using a thermocouple sensor at the endoscope tip (112 time points at 15 s intervals) and adapter (52 time points at 15 s intervals), comparing AST and conventional light sources. A thermal camera assessed the temperature of the light cable ends immediately upon disconnection. Light cables were held to standard surgical drapes immediately after disconnection, both with direct and indirect contact.ResultsAverage endoscope tip temperature was 24.0 °C for AST and 25.2 °C for conventional (p < 0.001). Average adapter temperature was 26.6 °C for AST and 27.3 °C for conventional (p = 0.003). Immediately upon disconnection, light cable temperature averaged 40.9 °C for cables attached to AST, versus 56.8 °C for conventional light sources. Conventional light cables showed notable drape burns at all time intervals with both direct and indirect contact. Damage was significantly greater with indirect contact via thermal radiation. The AST system did not burn drapes with either direct or indirect contact.ConclusionAST technology provides significant safety value by removing radiative heat transfer as a possible agent of patient and caregiver harm, rapidly lowering the temperature of an accidentally disconnected light cable to levels well below the threshold for causing skin injury and drape burns.

Mid infrared throughput using 5 μm apertures was investigated using micro-FTIR spectrometers with conventional light sources at two laboratories and the synchrotron radiation infrared (SR-IR) light source at SPring-8. With both the light sources micro-FTIR microscopy can analyze the fundamental O-H vibration in andesitic glass with 1 weight % H2O through 5 μm apertures. Spectra obtained at SPring-8 show better relative standard deviations due to the brighter and more highly collimated nature of SR-IR compared to conventional light sources. The spectra with 100 and 1000 scans at SPring-8 have similar relative standard deviations to those with 1000 and 10200 scans, respectively, at laboratories. The successful analysis with 5 μm apertures using both light sources shows the potential for an improvement in the spatial resolution of micro-FTIR analyses.

In this paper, we present new results on the controlled directional steering and focusing of surface plasmon polaritons (SPPs) via 1D and 2 D metagratings by changing the angle of incidence, the incident wavelength and polarization. These findings build on previous work of our group on polarization controlled steering of SPPS using fishbone meta gratings and greatly expand on the functionality of the latter using novel designs. First we show that by creating a running wave of polarization along a one dimensional metallic metagrating consisting of subwavelength spaced rotated apertures that propagates faster than the SPP phase velocity, we can generate surface plasmon wakes, which are the two-dimensional analogue of Cherenkov radiation. The running wave of polarization travels with a speed determined by the angle of incidence and the photon spin angular momentum. We utilize this running wave of polarization to demonstrate controlled steering of the wakes by changing both the angle of incidence and the polarization of light, which we measure through near-field scanning optical microscopy. Next we report a simple 2D metagrating design strategy that can be used for focusing, polarization beam splitting, waveguide coupling, and even phase control at the focus of an SPP beam. We experimentally verify our 2D metasurface by creating a four wavelength plasmonic demultiplexer, which also has polarization selectivity (on/off). The wavelength demultiplexer is designed such that each of the four wavelengths is focused to a different spot outside of the structure. Coupling of free space light to SPPs is achieved by milling subwavelength apertures into a thin gold film. This methodology can be easily extended to any wavelength where SPPs exist, for an arbitrary number of wavelengths, and with polarization selectivity and phase control at the focus as well. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Amid the growing global demand for sustainable crop production, plant factories with artificial lighting (PFALs) have gained attention as the systems provide stable, optimal growth environments for crops, and are largely unaffected by climate change. However, a limitation of widely used light-emitting diodes (LEDs) in PFALs is their decreased energy conversion efficiency at high output levels, prompting the search for more efficient light sources. This study focused on laser diodes (LDs), which has shown superior energy conversion efficiency, as an alternative. We developed an LD lighting system capable of mixing red and blue light at arbitrary ratios and mounted it onto a commercial gas-exchange measurement system. Using this system, photosynthetic parameters in rice were obtained under conditions of red light alone and as well as combined red and blue light illumination. Under red LD illumination alone, steady-state CO2 assimilation rate, stomatal conductance, and transpiration rate in rice were significantly higher than those under red LED illumination, whereas intrinsic water-use efficiency decreased due to a relatively greater increase in stomatal conductance. Notably, stomatal conductance and transpiration rate exhibited pronounced temporal oscillations with a period of approximately 900 s, which closely corresponded to oscillations in stomatal aperture confirmed by microscopic observations. Under combined red and blue LD illumination, steady-state photosynthetic parameters did not differ significantly from those under LED illumination; however, the dominant oscillatory frequency observed under red LD alone was not detected, and some photosynthetic capacity parameters tended to decline. Furthermore, CO2 response analyses revealed that, despite lower CO2 assimilation, stomatal conductance responded more strongly to changes in intercellular CO2 concentration under combined red and blue LD illumination. Taken together, these results demonstrate that LD lighting, particularly red LD, enhances stomatal dynamics and induces characteristic oscillatory behavior compared with LED lighting. While red LD appears to be a promising cultivation light source for PFALs capable of maintaining high photosynthetic activity, the physiological impacts associated with blue LD, including potential reductions in photosynthetic capacity, require further study to optimize blue-light proportions for rice cultivation.

Underwater wireless communications, have more attention day after day, due to their wide applications in the military, and in the scientific community. It is also useful in vehicles and devices that are deployed underwater which are difficult to connect with wires. Acoustic communications mostly used underwater technology nowadays, this technology suffers from limited bandwidth and capacity, and for this reason, a complementary technology like underwater wireless optical communication (UOWC) is to be in the field. In this paper, we simulated the UOWC system with Optisystem software to measure the maximum distances in different underwater mediums. In this simulation, three types of seawater are used: pure seawater, Coastal Ocean, and turbid harbor. The intensity modulation for the message signal was performed using a Mach-Zehnder Modulator and Laser Diode as the light source. Results were compared between the wavelength at the beginning of the visual light spectrum and the wavelengths that have the minimum attenuation in the same visual spectrum, in terms of the transmitting distance and the transmitting power. A signal was sent for more than 100 m in clear ocean water with 1 mW, while the same type of water signal was sent for the same distance with 0.35 mW (65% saving) using different operating wavelengths.

Compact high-efficiency ultraviolet solid-state light sources--such as light-emitting diodes (LEDs) and laser diodes--are of considerable technological interest as alternatives to large, toxic, low-efficiency gas lasers and mercury lamps. Microelectronic fabrication technologies and the environmental sciences both require light sources with shorter emission wavelengths: the former for improved resolution in photolithography and the latter for sensors that can detect minute hazardous particles. In addition, ultraviolet solid-state light sources are also attracting attention for potential applications in high-density optical data storage, biomedical research, water and air purification, and sterilization. Wide-bandgap materials, such as diamond and III-V nitride semiconductors (GaN, AlGaN and AlN; refs 3-10), are potential materials for ultraviolet LEDs and laser diodes, but suffer from difficulties in controlling electrical conduction. Here we report the successful control of both n-type and p-type doping in aluminium nitride (AlN), which has a very wide direct bandgap of 6 eV. This doping strategy allows us to develop an AlN PIN (p-type/intrinsic/n-type) homojunction LED with an emission wavelength of 210 nm, which is the shortest reported to date for any kind of LED. The emission is attributed to an exciton transition, and represents an important step towards achieving exciton-related light-emitting devices as well as replacing gas light sources with solid-state light sources.

Laser Speckle Imaging recently has become a promising tool to assess fruit quality and can be applied in fruit sorting. It is a non-destructive, optical method which uses light scattered of fruit surface after illuminated by laser light. Laser speckle imaging methods use He-Ne laser or diode laser as the light source yet both lasers have differences in performance and price. Diode lasers are more preferable due to their efficiency, low cost, small and compact, and varied wavelength. In this research, an optical system which consisted of a laser source and a CMOS camera was used for Laser Speckle Imaging. A 632,8 nm He-Ne laser and a 650 nm diode laser were used, their performances were compared. The samples were two kinds of apples, &lt;em&gt;Red Delicious&lt;/em&gt; and &lt;em&gt;Fuji,&lt;/em&gt; five samples for each cultivar. The laser light was expanded using a beam expander hence illuminated on the apple surface at 30&lt;sup&gt;o&lt;/sup&gt; angle. A monochrome Thorlabs CMOS camera with camera lens was used to record the speckle patterns of the apple surface. Both lasers were kept at the same laser power by Neutral Density Filters. ImageJ software was used to calculate the gray value of the speckle pattern for each sample, the speckle gray values were compared for different laser light sources and apple types. The results showed that there is a significant difference in gray value level between both apples. Higher maximum gray values were found on the &lt;em&gt;Fuji&lt;/em&gt; apples compared to the Red Delicious apples which were about 21.7 % when using He-Ne laser and 18.3 % when using diode laser. Higher maximum gray value for Fuji apples could be due to their rounder shape, firmer skin and flesh, they scatter more light. The curvature and the firmness of the fruits affected the gray value level. For each apple type, there was a slight difference in maximum gray values for both laser sources. Higher gray values were obtained when using diode laser compared to the He-Ne laser, 22.0 % difference for Fuji apples and 25.2 % difference for Red Delicious apples. These could be because of the less coherence, wider bandwidth, and irregular beam shape of the diode laser that it scatters more light and suppresses speckles.

Fast and high-resolution simultaneous measurement of temperature and strain is experimentally demonstrated. A Fabry–Perot interferometer fabricated in a polarization-maintaining fiber has sharp transmission peaks, which are divided into two sets corresponding to the polarization of the transmitted light. The sharp transmission peaks shift in response to changes in temperature and strain, and because the dependence coefficients are different for each set, temperature and strain can be simultaneously measured with high resolution. To read the position of a sharp transmission peak, wavelength sweeping with narrowband light is necessary. By using injection current modulation in a laser diode, high-speed wavelength sweeping and short measuring time are realized. We performed simultaneous measurements with a measurement time of 20 $\mu$ s; measurement resolution of 0.1 $^\circ$ C and 0.8 $\mu \epsilon$ for temperature and strain, respectively; and noise spectral density of 30 n $\epsilon /\sqrt{\rm Hz}$ . We further experimentally demonstrated that vibration with an amplitude of 20 $\mu \epsilon$ and a frequency of 1 Hz and heating at a rate of 0.7 $^\circ$ C $/$ s can be simultaneously measured.

This clinical study assessed photobiomodulation (PBM) induced analgesic effects of diode lasers and an LED light source on the dental pulp. Baseline responses to electric pulp testing (EPT) were recorded in 93 healthy unrestored premolar teeth in 26 adults (age range 22–63 years) attending a private dental practice. The teeth were irradiated on buccal and lingual aspects of the crown, by placing the tips on the middle third of the crown of the teeth, on separate days for each of 4 different light sources (660, 808, or 904 nm diode lasers, or a novel multi-wavelength LED light source (700–1100 nm)) using comparable parameters (100 mW, 30 s, 6 J). EPT scores were measured after a further 1-, 2-, 5- and 20-min. Discomfort caused by PBM therapy was recorded using the Wong-Baker scale. EPT changes were tracked over time using repeated measures analysis of variance. Baseline EPT scores were very consistent between different days (linear regression r2 0.9422–0.9648). All PBM devices caused a significant elevation in EPT at 5 min, with an earlier onset at 2 mins for 904 nm and LED. The LED was the only light source that elevated scores at 20 min. Across 2–20 min, when ranked by effectiveness, the greatest EPT elevations were seen for LED, followed by 904 nm, then 660 nm and finally 808 nm. Discomfort during PBM was most common with 904 nm, followed by 808 nm. No discomfort occurred from the LED. Among the light sources utilized, the LED multi-wavelength system demonstrated the largest increase in EPT readings, suggesting its potential as a non-pharmacological alternative for achieving dental analgesia compared to diode lasers.

Near-infrared spectroscopy (NIRS) based techniques are utilised in quantifying changes of chromophore concentrations in tissue. Particularly, non-invasive in vivo measurements of tissue oxygenation in the cerebral cortex are of interest. The measurement method is based on illuminating tissue and measuring the back-scattered light at wavelengths of interest. Tissue illumination can be realised using different techniques and various light sources. Commonly, lasers and laser diodes (LD) are utilised, but also high-power light emitting diodes (HPLED) are becoming more common. At the moment, a wide range of available narrow-band light sources exists, covering basically the entire spectrum of interest in brain tissue NIRS measurements. In this paper, in the centre of our interest are LDs and HPLEDs, because of their affordability, efficiency in terms of radiant flux versus size and easiness to adopt in in vivo medical applications. We compare characteristics of LDs and HPLEDs at specific wavelengths and their suitability for in vivo quantifying of different tissue chromophore concentration, particularly in cerebral blood flow (CBF). A special focus is on shape and width of the wavelength bands of interest, generated by the LDs and HPLEDs. Moreover, we experimentally study such effects as, spectroscopy cross talk, separability and signal-to-noise ratio (SNR) when quantifying tissue chromophore concentration. Chromophores of our interest are cytochrome, haemoglobin and water. Various LDs and HPLEDs, producing narrow-band wavelengths in the range from 500 nm to 1000 nm are tested.

This study proposes an improved hybrid scheme of spectral polarization coding SPC and spectral amplitude coding SAC based on a specified orthogonal ternary sequence. In a previous SPC scheme, the entire wavelength was assigned either a vertical or a horizontal state of polarization. However, this study assigns positive, negative, or null chip values to individual wavelengths to create an orthogonal ternary sequence based on the bipolar Walsh-Hadamard matrix. This approach reduces the number of wavelength collisions at the photodetector and hence reduces the phase-induced intensity noise PIIN. Neglecting the effects of shot noise and thermal noise, we consider only PIIN with a degree of polarization P=0. The proposed scheme improves the bit error rate by 40% and 100% over SPC and complementary unipolar SAC schemes. The number of simultaneous active users supported by the hybrid scheme for the worst case P=1 is improved by 41.3% over the complementary unipolar SAC coding scheme for the ideal case P=0. © 2007 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.2432883 Subject terms: optical code-division multiple-access; hybrid spectral polarization and amplitude coding; fiber Bragg grating; polarization beamsplitter; multiple- access interference; phase-induced intensity noise.