Optical Loss Measurements Research Articles

Precise Reflectance/Transmittance Measurements of Highly Reflective Optics with Saturated Cavity Ring-Down Signals

In this paper, a data processing approach was developed to accurately extract the ring-down time and amplitude of the saturated cavity ring-down (CRD) signal; both were utilized to determine simultaneously the high reflectance and residual transmittance of highly reflective (HR) mirrors with a dual-channel CRD configuration. The influence of saturation was eliminated by deleting the beginning saturated data points of the saturated CRD signal and fitting the remaining non-saturated CRD signal to a single-exponential function. By comparing the reflectance/transmittance measurement results of HR samples obtained via data processing of saturated CRD signals and via single-exponentially fitting non-saturated CRD signals with utilization of neutral density filter(s) to eliminate saturation, it was found that the reflectances obtained with both methods were in excellent agreement, while the residual transmittance obtained with the saturated CRD signal was more accurate than that obtained with the neutral-density-filter-attenuated non-saturated CRD signal. The proposed data processing method eliminated the need to use the neutral density filters, therefore avoiding the adding of the optical density error to the uncertainty of residual transmittance measurement and improving the measurement accuracy. The proposed data processing method also extended the dynamic range of the dual-channel CRD scheme for simultaneous measurement of reflectance, transmittance and optical loss.

Insights into the dielectric function of plant leaves under water stress.

In this work, we present a practical approach combining experimental and theoretical analyses to assess water evaporation in Arabica coffee leaves. We examine continuously the changing water content of leaves through optical reflectance spectroscopy and mass loss measurements, beginning from a fully saturated stage and extending beyond the turgor loss point. We establish a relationship between the current water content and the dielectric function, based on the changing of the molecular water dipoles inside the leaf due to evaporation.

Degradation Analysis of Single-Mode and Multimode Fibers in a Full-Scale Wellbore and Its Impact on DAS and DTS Measurements

Distributed fiber optic sensors (DFOS) are viewed as a promising technology for efficient, cost-effective, and non-intrusive real-time monitoring for a variety of applications. The chemical passivity, non-magnetic interference behavior, and ability to acquire continuous measurements at high-spatial resolution have made DFOS very attractive for in-situ measurement of temperature, strain, vibration, etc. The accuracy of the measured parameter by the DFOS is highly dependent on the strength and quality of the optical signal returning from the point of interest. The signal degradation in DFOS results from optical losses due to attenuation, absorption, scattering, bending, dispersion, and coupling. This study analyzes the degradation observed in both the single-mode and multimode fibers installed in a 1574 mdeep wellbore for acquiring distributed acoustic sensing (DAS) and distributed temperature sensing (DTS) data, respectively. The degradation was unexpected as it was observed within three years of DFOS installation in an experimental, non-producing well that contains non-corrosive fluids and operates in a low-temperature (<54.4 °C) and low-pressure (<3500 psi or 24131 kPa) environment. A root-cause analysis was performed to investigate the cause of this degradation using time-lapse optical loss measurements acquired at different wavelengths using an optical time-domain reflectometer. Degradation of the multimode fiber was also examined by the time-lapse analysis of the Raman backscatter that is used for DTS measurement. Based on the investigation, microbending was found to be the main cause of the observed degradation. Its impact on the quality of the DAS and DTS measurements was also analyzed both qualitatively and quantitively. Recommendations for minimizing degradation are presented.

Effects of UV treatment on the properties of ultra-thin indium tin oxide films during growth and after deposition by cavity ring-down spectroscopy

In this work, an ultra-sensitive optical absorption technique based on Cavity Ring-Down Spectroscopy (CRDS) was employed to study the effects of UV treatment on the optical properties of ultra-thin indium tin oxide (ITO) films. The ITO films were submitted to UV treatment either after the deposition process or in-situ during the thin-film growth process. Different flow rates of oxygen in the vacuum chamber during film growth were also investigated. An ITO-coated glass substrate inserted in the CRDS cavity at a Brewster’s angle provided a ring-down time of about 1.6 µs, which enabled measurements of optical absorption loss as small as 3 × 10−6. To compare the effects of the UV film treatment, the CRDS technique was employed to measure the extinction coefficient for samples coated with and without the UV treatment. While the optical absorption data was being collected, the electrical resistivity was also simultaneously monitored. The post-deposition UV treatment was found to improve the optical transparency and the electrical performance of ITO film; the optical extinction coefficient of the ultra-thin ITO film is shown to decrease by about 24%. The in-situ UV treatment during growth is also shown to consistently increase the optical transparency of the ultra-thin ITO films and providing outstanding optical performance especially for high flow rates of oxygen during film growth. The electrical resistivity for oxygen flow rates in the range 0.6 - 1.4 sccm is also improved by the in-situ UV treatment, however it shows a sharp increase for oxygen flow rates beyond 1.4 sccm. The CRDS platform is demonstrated here to provide a highly accurate and sensitive methodology for measurement of minute optical absorption losses in ultra-thin films that typically cannot be precisely measured using other conventional spectrophotometric techniques.

Mobile internet big data technology-based echo loss measurement method of optical communication system

The paper proposes a method to analyze the process of echo loss in an optical communication system in combination with mobile internet big data technology. The optical echo loss tester shall include the output connector, the standard reflector and the automatic unite to process and display the device to be measured. Using mode-coupling theory, we can calculate the loss when a light in an optical fiber flows through a fiber optic connector under various effect variables; then analytical formulas are developed, to calculate insertion and echo loss in a real-life situation. In this research, we propose a method for measuring echo loss in optical communication systems using mobile internet big data technology. The effect of this method is evaluated combined with the simulation test, based on the research carried out by research. The optical communication echo loss measurement based on mobile Internet of Things big data technology has some influence.

Detection of OPGW Water Immersion Faults by 1.24/1.625 µm Optical Transmission Loss Measurement

Detection of OPGW Water Immersion Faults by 1.24/1.625 µm Optical Transmission Loss Measurement

Experimental investigation of mid-infrared Er:ZBLAN fiber laser

In this contribution the diode pumped high-power Er:ZBLAN laser operating at around 2.8 µm is reported. The laser produces 2 W output power with the slope efficiency of 24 % measured with respect to the incident pump power. Full Text: PDF ReferencesS. D. Jackson, "Towards high-power mid-infrared emission from a fibre laser", Nature Photonics 6, 423 (2012). CrossRef V. Portosi, D. Laneve, C. M. Falconi, and F. Prudenzano, "Advances on Photonic Crystal Fiber Sensors and Applications", Sensors 19, (2019). CrossRef M. C. Falconi, D. Laneve, and F. Prudenzano, "Advances in Mid-IR Fiber Lasers: Tellurite, Fluoride and Chalcogenide", Fibers 5, 23 (2017). CrossRef M. Michalska, P. Grześ, J. Świderski, "High power, 100 W-class, thulium-doped all-fiber lasers", Phot. Lett. Poland, 11, 109 (2019). CrossRef Y. O. Aydin, V. Fortin, R. Vallée, and M. Bernier, "Towards power scaling of 2.8 μm fiber lasers", Opt. Lett. 43, 4542 (2018). CrossRef S. Crawford, D. D. Hudson, and S. D. Jackson, "High-Power Broadly Tunable 3- μm Fiber Laser for the Measurement of Optical Fiber Loss", IEEE Photonics Journal 7, 1 (2015). CrossRef V. Fortin, F. Jobin, M. Larose, M. Bernier, and R. Vallée, "10-W-level monolithic dysprosium-doped fiber laser at 3.24 μm", Opt. Lett. 44, 491 (2019). CrossRef L. Sójka, et al., "Experimental Investigation of Mid-Infrared Laser Action From Dy3+ Doped Fluorozirconate Fiber", IEEE Photon. Technol. Lett. 30, 1083 (2018). CrossRef M. Pollnan and S. D. Jackson, "Erbium 3 /spl mu/m fiber lasers", IEEE J. Sel. Top. in Quantum Electron., 7, 30 (2001). CrossRef Y. O. Aydin, F. Maes, V. Fortin, S. T. Bah, R. Vallée, and M. Bernier, "Endcapping of high-power 3 µm fiber lasers", Opt. Express 27, 20659 (2019). CrossRef C. A. Schäfer, "Fluoride-fiber-based side-pump coupler for high-power fiber lasers at 2.8 μm", et al., Opt. Lett. 43, 2340 (2018). CrossRef O. Henderson-Sapir, J. Munch, and D. J. Ottaway, "New energy-transfer upconversion process in Er3+:ZBLAN mid-infrared fiber lasers", Opt. Express 24, 6869 (2016). CrossRef F. Maes, V. Fortin, S. Poulain, M. Poulain, J.-Y. Carrée, M. Bernier, and R. Vallée, "Room-temperature fiber laser at 3.92 μm", Optica 5, 761 (2018). CrossRef R. I. Woodward, M. R. Majewski, D. D. Hudson, and S. D. Jackson, "Swept-wavelength mid-infrared fiber laser for real-time ammonia gas sensing", APL Photonics 4, 020801 (2019). CrossRef M. Kochanowicz, et al., "Near-IR and mid-IR luminescence and energy transfer in fluoroindate glasses co-doped with Er3+/Tm3+", Opt. Mater. Express 9, 4772 (2019). CrossRef M. Kochanowicz, et al., "Sensitization of Ho3+ - doped fluoroindate glasses for near and mid-infrared emission", Optical Materials 101, 109707 (2020). CrossRef J. Wang, X. Zhu, M. Mollaee, J. Zong, and N. Peyhambarian, "Efficient energy transfer from Er3+ to Ho3+ and Dy3+ in ZBLAN glass", Opt. Express 28, 5189 (2020). CrossRef M. C. Falconi, D. Laneve, V. Portosi, S. Taccheo, and F. Prudenzano, "Design of a Multi-Wavelength Fiber Laser Based on Tm:Er:Yb:Ho Co-Doped Germanate Glass", J Lightwave Technol 1 (2020). CrossRef K. Anders, A. Jusza, P. Komorowski, P. Andrejuk, and R. Piramidowicz, "Short wavelength up-converted emission studies in Er3+ and Yb3+ doped ZBLAN glasses", J. Lumin. 201, 427 (2018). CrossRef P. Komorowski ,K. Anders ,U. Zdulska,R. Piramidowicz R. "Erbium doped ZBLAN fiber laser operating in the visible - feasibility study", Photonics Lett Pol 9, 85 (2017). CrossRef J. Swiderski, M. Michalska, and P. Grzes, "Broadband and top-flat mid-infrared supercontinuum generation with 3.52 W time-averaged power in a ZBLAN fiber directly pumped by a 2-µm mode-locked fiber laser and amplifier", Applied Physics B 124, 152 (2018). CrossRef V. Fortin, M. Bernier, S. T. Bah, and R. Vallée, "30 W fluoride glass all-fiber laser at 2.94 μm", Opt. Lett. 40, 2882 (2015). CrossRef

Vertically tapered waveguide spot size converters fabricated via a linewidth controlled grey tone lithography for InP-based photonic integrated circuits.

We report a novel and simple fabrication process to realize vertically tapered spot size converters (SSC) on InP photonic integrated circuits. The vertical tapering was achieved via a linewidth controlled local optical dose variation, leading to a grey tone photoresist profile. The fabricated SSCs are compact, polarization insensitive and demonstrate a very high mode conversion efficiency of 95%. Integrated SSCs improved the overall loss by 5 dB giving a coupling loss as low as 1.3 dB/facet, for a lensed fibre with a mode field diameter of 3.0 µm. A good agreement was found between the fibre-to-fibre optical loss measurements and those predicted from simulations.

Advances in distributed vibration sensing for optical communication fiber state visualization

This paper describes our recently proposed novel distributed vibration sensing (DVS) measurement technologies for visualizing the state of optical fiber in communication cables. Conventional fault location of optical fiber cable involves the measurement of just optical loss. However, in recent years, attempts have been made to visualize optical fiber attributes that cannot be observed with conventional technology; a key technique is measuring the distribution of dynamic strain caused by vibration. Accurately capturing the vibration makes it possible to measure the state of various fibers that cannot be realized with conventional loss measurements. In measuring vibration, it is necessary to measure not only the power of the light but also several physical parameters such as the vibrational frequency, which is the time variation of the waveform of scattered light, and the phase of the light itself. In addition, it is also necessary to consider the conventional specifications of optical loss measurement techniques, such as distance resolution and measurement distance, which have been considered in the past. In this paper, we introduce several DVS technologies and show their applicability to various state detection schemes for communication fibers.

Исследование пространственной и токовой динамики оптических потерь в полупроводниковых лазерных гетероструктурах методом оптического зондирования

The spatiotemporal dynamics of optical losses and carrier density in a heterostructure of a semiconductor laser with a segmented contact were studied using an optical probe technique based on the coupling of probe radiation with a wavelength of 1560 nm into a semiconductor laser chip under investigation based on an AlGaAs/ InGaAs/ GaAs heterostructure and emitting at a wavelength of 1010 nm. It has been shown that the use of a probe beam with a wavelength of 1560 nm makes it possible to ensure the sensitivity of the measurement of internal optical losses of no worse than 1 cm-1. The use of a segmented design of the current pumping region made it possible to estimate the absolute value of internal optical losses. It was shown that a change in the configuration of the Fabry-Perot eigenmodes of the laser affects the distribution of charge carriers and internal optical losses both in the current pump region and in the passive part of the laser chip that is not pumped by the current.

Measurements of internal optical loss inside an operating laser diode

An experimental technique for measuring internal optical loss in high-power edge-emitting semiconductor lasers is demonstrated. The technique is based on coupling a probe beam into the waveguide of a pulse-pumped laser diode. It allows measuring free-carrier absorption (FCA) in a laser heterostructure at different temperatures and at pump current levels up to 30 kA/cm2. Measurement results are presented for two laser heterostructure designs, which vary in the waveguide doping level and material. For both heterostructures, the pump current increase induces a significant rise in FCA and a corresponding increase in internal optical loss, from 0.4–0.7 cm−1 at the threshold current to 2–2.5 cm−1 at 15 kA/cm2. At higher temperatures, the dependence is even stronger and the internal optical loss rises to 6 cm−1 (65 °C, 27 kA/cm2). The gradient of the FCA current dependence is lower for the laser heterostructure with a doped GaAs waveguide, while the heterostructure with an undoped AlGaAs waveguide displays a larger increase in FCA but better internal quantum efficiency at high currents. These results show that the proposed experimental method has significant potential.

Study and Analysis of Light Scattering Loss in Irregular Integrated Optical Waveguides

Results are presented that have been obtained in numerical and experimental investigations of three-layer single-mode and multimode polystyrene, liquid, and liquid-crystal integrated optical waveguides. Numerical simulation results are presented and compared to the experimental data. The form of the scatter diagram from both the coordinates of the observation points and the waveguide phase slow-down factor is investigated. Characteristic experimental scatter diagrams in the plane transverse to the plane of incidence are given for TE- and TM-polarization. Calculated and experimental scatter diagrams are found to be in satisfactory agreement. Measurement of optical loss in the waveguides has allowed determining, in particular, the root-mean-square roughness height of the substrates of the polystyrene and liquid waveguides, which fairly corresponds to the known surface finish. In the liquid-crystal waveguide, the investigations have been focused on the features of the TE- and TM-mode scattering in a wide range of the phase slow-down factor variation. Complicated nonlinear processes of radiation field transformation beyond the waveguide are observed experimentally and through numerical simulation. Statistical parameters obtained for the irregularities of the investigated waveguides are presented. In addition, the root-mean-square estimates are given for spatial fluctuations of the director and compared to the average correlation radius for fluctuations of local orientation of nematic liquid crystal molecules.

Ultranarrow-waveguide AlGaAs/GaAs/InGaAs lasers

We have designed, fabricated and studied ultranarrow-waveguide heterostructure lasers emitting in the spectral range 1000 – 1100 nm. The lasers have been characterised by current – voltage, light – current, far-field intensity distribution and internal optical loss measurements. The ultranarrow-waveguide lasers have been shown to have a threshold current density of ∼75 A cm−2, internal quantum efficiency near 100 % and internal optical loss near the lasing threshold under 1 cm−1, which corresponds to the level of standard heterostructures. We have demonstrated the possibility of obtaining up to 5 W of output power in continuous mode and up to 30 W in pulsed mode, with a beam convergence (FWHM) of 17.8°. The slope of the internal optical loss as a function of pump current for the ultranarrow-waveguide lasers can be markedly lower than that in lasers with a standard design, but internal quantum efficiency drops to 40 % with increasing pump current. The use of barrier layers in ultranarrow-waveguide lasers makes it possible to substantially reduce the drop in internal quantum efficiency.

Comparison of photothermal responses under spatial and temporal modulations of CW Gaussian beam excitation: A numerical study

Obtaining stronger photothermal response of optical materials is of great interest in the measurement of optical losses using the photothermal tools, in particular the thermal mirror. In our previous work, we experimentally demonstrated a more effective method of thermal mirror detection employing the spatial modulation (SM) of a continuous wave Gaussian beam excitation instead of the conventional temporal modulation (TM). A complete analytical model is presented to describe the laser-induced three-dimensional dynamic thermal fields in a semi-infinite sample and the time-dependent thermal mirror due to the thermoelastic response of the material as well as the evolution of the intensity distribution of a probe beam after interacting with the thermal mirror, in both the SM and TM schemes under the low absorption and exponentially-decaying absorption cases. With the model, we obtained the variations of temperature, surface displacement, and diffraction intensity giving rise to the photothermal response of the material. The results of the comparison between the two schemes reveal that the SM scheme is more sensitive than the TM scheme originating from a large variation range of the temperature in the SM scheme. We also explained the complex relation between the surface displacement and the diffraction intensity of the probe beam at the center of the detection plane on the basis of the phase shift caused by the thermal mirror. The presented model and the results of comparison are of great importance to gain a deeper insight into the photothermal characterization in both the SM and TM schemes.

Polymer optical bridges for efficient splicing of optical fibers

We present an application of optonumerical methodology for improvement of functional parameters of polymer optical bridges that connect two optical fibers. To fully determine and improve the properties of this kind of microstructure, experimental methods are combined with numerical modeling. The parameters describing the functionality of the polymer optical bridges are optical losses (insertion and return), which determine the usability of those elements as optical fiber splices. These parameters are the function of such features as refractive index distribution, microstructure geometry, and propagation of the light wavelength. To analyze the relation of those features on the functional parameters of the studied microstructures, the experimental results are compared to the ones obtained with simulations. Numerical modeling of the aforementioned optical bridges is performed by means of the finite-difference time-domain method. Experimental methods consist of optical diffraction tomography, which is used to obtain a full three-dimensional refractive index distribution of optical bridge, and measurement of optical losses. Implementation of the proposed methodology in iterative procedure allows the optimization of the fabrication procedure to produce efficient and reliable optical splices with desired functional parameters—insertion loss at the level of 0.2 dB and return loss above 60 dB.

Deuterium retention and erosion in liquid Sn samples exposed to D2 and Ar plasmas in GyM device

The use of tin (Sn) as a liquid metal for plasma facing components has been recently proposed as a solution to the high heat load issue on the divertor target plates in nuclear fusion reactors. Due to its low vapor pressure, low reactivity with hydrogen and good resilience to neutron impact, tin is a good candidate as plasma facing component. However its high atomic number poses concerns about plasma contamination.In this paper two fundamental aspects have been investigated: deuterium retention and erosion fluxes from the Sn surface towards the plasma. The samples were exposed to plasma inside the linear machine GyM in magnetic cusp configuration. This setup permits to expose free liquid specimens without the need for the Capillary Porous System. Moreover it permits to lower the magnetic field in order to increase Sn Larmor radius and consequently limit Sn re-deposition in erosion experiments.Ex-situ analyses by ion beam diagnostics on solid samples exposed to deuterium plasma have proved that the amount of retained atomic deuterium is very low, approximately 0.18 at% estimated by Nuclear Reaction Analysis and 0.25 at% estimated by Elastic Recoil Detection Analysis.In the framework of erosion studies, the spectroscopic parameter S/XB was evaluated in Ar plasma for the SnI line at 380.1 nm by Optical Emission Spectroscopy and mass loss measurements in the 5–11 eV Te range, at a density ne ∼ 1.5 × 1011 cm−3. An average value of 150 ± 23 was obtained.

Measurement of optical losses in a high-finesse 300 m filter cavity for broadband quantum noise reduction in gravitational-wave detectors

Earth-based gravitational-wave detectors will be limited by quantum noise in a large part of their spectrum. The most promising technique to achieve a broadband reduction of such noise is the injection of a frequency dependent squeezed vacuum state from the output port of the detector, whit the squeeze angle rotated by the reflection off a Fabry-Perot filter cavity. One of the most important parameters limiting the squeezing performance is represented by the optical losses of the filter cavity. We report here the operation of a 300 m filter cavity prototype installed at the National Astronomical Observatory of Japan (NAOJ). The cavity is designed to obtain a rotation of the squeeze angle below 100 Hz. After achieving the resonance of the cavity with a multi-wavelength technique, the round trip losses have been measured to be between 50 ppm and 90 ppm. This result demonstrates that with realistic assumption on the input squeeze factor and on the other optical losses, a quantum noise reduction of at least 4 dB in the frequency region dominated by radiation pressure can be achieved.

Low Loss Atomic Layer Deposited Al2O3 Waveguides for Applications in On-Chip Optical Amplifiers

We present the growth and optimization of ultralow loss Si-based Al2O3 planar waveguides, which have a high potential to boost the performance of rare-earth ion doped waveguide devices operating at visible and C-band wavelength ranges. The planar waveguide structures are grown using thermal atomic layer deposition. Systematic characterization of the obtained thin films is performed by spectroscopic ellipsometry, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses, and the optimum parameters are identified. The optical loss measurements for both transverse electric (TE) and transverse magnetic polarized light at 633, 829, and 1549 nm are performed. The lowest propagation loss value of 0.04 ± 0.02 dB/cm for the Al 2O3 waveguides for TE polarization at 1549 nm is demonstrated.

Broadband and high resolution measurements of cavity loss and dispersion

We present a method for broadband measurements of dispersion and loss of an optical cavity. We employ an optical frequency comb directly coupled into a cavity to scan the cavity modes and retrieve their shapes and positions. The measurement data is acquired using instrumental-line-shape-free Fourier transform spectrometry. This method can be developed into a powerful tool for optical loss and dispersion measurements for broadband characterization of optical elements as well as absorption and dispersion spectroscopy. Full Text: PDF ReferencesTh. Udem, R. Holzwarth, T.W. Hänsch, "Optical Frequency Metrology", Nature 416, 233–237 (2002). CrossRef R.A. McCracken, J.M. Charsley, D.T. Reid "A decade of astrocombs: recent advances in frequency combs for astronomy", Optics Express 25, 13, 15058-15078 (2017). CrossRef M.J. Thorpe, D. Balslev-Clausen, M.S. Kirchner, J. Ye, "Cavity-enhanced optical frequency comb spectroscopy: application to human breath analysis", Optics Express 16, 4, 2387-2397 (2008). CrossRef J. Domysławska et al., "Cavity ring-down spectroscopy of the oxygen B-band with absolute frequency reference to the optical frequency comb", The Journal of Chemical Physics 136, 024201 (2012). CrossRef P. Masłowski K.C. Cossel, A. Foltynowicz, J. Ye., "Cavity-Enhanced Direct Frequency Comb Spectroscopy", in G. Gagliardi and H.-P. Loock, "Cavity-Enhanced Spectroscopy and Sensing", Springer (2014). CrossRef L. Rutkowski et al., "Sensitive and broadband measurement of dispersion in a cavity using a Fourier transform spectrometer with kHz resolution", Optics Express Vol. 25, Issue 18, pp. 21711-21718 (2017). CrossRef E.D. Black, "An introduction to Pound-Drever-Hall laser frequency stabilization", American Journal of Physics 69, 79 (2001) CrossRef A. Cygan et al., "One-dimensional frequency-based spectroscopy", Optics Express. 23, 14472. 10.1364 ( 2015). CrossRef P. Masłowski et al., "Surpassing the path-limited resolution of Fourier-transform spectrometry with frequency combs", Phys. Rev. A 93, 021802(R) (2016). CrossRef L. Rutkowski, P. Masłowski, A.C. Johansson, A. Khodabakhsh, A. Foltynowicz, "Optical frequency comb Fourier transform spectroscopy with sub-nominal resolution and precision beyond the Voigt profile", Jour. of Quant. Spect. and Rad. Trans., 204, 63-73 (2018). CrossRef S. Schiller, "Spectrometry with frequency combs," Opt. Lett. 27, 766-768 (2002). CrossRef A. Cygan et al., "Absolute molecular transitions frequencies measured by three cavity-enhanced spectroscopy techniques" J. Chem. Phys. 144 214202-1-214202-11 (2016). CrossRef I.E. Gordon et al., "The HITRAN2016 Molecular Spectroscopic Database", J. Quant. Spect. Radiat. Trans. (2017). CrossRef

The properties of free-standing epoxy polymer multi-mode optical waveguides

The paper reports on the fabrication and characterisation of free-standing multimode optical epoxy polymer waveguides consisting of a core made of EpoCore and EpoClad polymer cladding and cover protection layers. The 50 × 50 μm2 rectangular waveguides are intended for short-reach optical interconnection and optimised for an operating wavelength of 850 nm. The waveguides of the proposed shapes were fabricated by a standard photolithography process on a silicon substrate provided with a Poly(vinyl alcohol) thin layer. The free-standing structure was then achieved by peeling the deposited EpoClad/EpoCore/EpoClad structures of that substrate. The optical scattering losses of the created planar waveguides, measured by the fibre probe technique at 632.8 and 964 nm, were 0.30 dB cm−1 at 632.8 nm and 0.17 dB cm−1 at 964 nm. Propagation optical loss measurements for rectangular waveguides were performed by the cut-back method and the best samples had optical losses below 0.55 dB cm−1 at 850 and 1310 nm.