Mid-Infrared Chalcogenide Waveguides for Real-Time and Non

Subscriber access provided by YORK UNIV

Article

Mid-Infrared Chalcogenide Waveguides for Real-Time and Non-Destructive Volatile Organic Compounds Detection Tiening Jin, Junchao Zhou, Hao-Yu Greg Lin, and Pao Tai Lin Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.8b03004 • Publication Date (Web): 05 Dec 2018 Downloaded from http://pubs.acs.org on December 6, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Analytical Chemistry

Mid-Infrared Chalcogenide Waveguides for Real-Time and Non-Destructive Volatile Organic Compounds Detection Tiening Jin,a,b,c Junchao Zhou,a,b,c Hao-Yu Greg Lin,d and Pao Tai Lin a,b,c,* a. Department of Electrical and Computer Engineering, b. Department of Materials Science and Engineering, c. Center for Remote Health Technologies and Systems, Texas A&M University, College Station, Texas 77843, United States. d. Center for Nanoscale Systems, Harvard University, 11 Oxford Street, Cambridge, Massachusetts 02138, United States. ABSTRACT: A mid-infrared (mid-IR) sensor chip was demonstrated for volatile organic compounds (VOCs) detection. The sensor consisted of As2Se3 optical waveguides built by microelectronic fabrication processes. The VOCs sensing performance was characterized by measuring acetone and ethanol vapors at their characteristic C-H absorption from λ = 3.40 to 3.50 µm. Continuous VOCs detection with < 5 s response time was achieved by measuring the intensity attenuation of the waveguide mode. The miniaturized non-invasive VOCs sensor can be applied to breath analysis and environmental toxin monitoring.

VOCs are a wide range of carbon-based and organic chemical compounds emitted from various man-made or natural solids, liquids, and gases. 1-3 They are evaporated at room temperature due to their low boiling points. Though VOCs exist widely throughout our surroundings, some of them are harmful and even fatal to humans and can result in permanent environmental damage. 4-8 Exposure to high concentrations of VOCs causes throat irritation, headaches, and internal organ damage. 9 Continuous and low-level exposure can also cause long-term health effects. On the other hand, VOCs are biomarkers for various diseases and have been utilized to monitor health conditions. 10-12 Acetone, for example, is widely used as a biomarker for diabetes since it is found in the exhaled breath of diabetes patients. 13 The glucose level of patients can be traced by measuring the acetone concentration of the breath. Similarly, VOCs detection provides an efficient and accurate method to monitor human health and to trace environmental toxins. Currently, gas chromatography mass spectrometry (GC-MS) is the most prevalent method to analyze VOCs. 14-17 However, it is a bulky and time-consuming instrument because GC takes several minutes to separate different gases. The time delay during analysis is a challenge for instantaneous VOCs measurement. In addition, MS utilizes delicate ionization processes to identify chemicals, making it an expensive tool. Metal oxide semiconductors (MOS) are another method widely applied in VOCs detection. 18-20 The resistance of MOS changes in the presence of VOCs because there is a charge transfer between the surface and the chemisorption oxygen. This solid-state sensor has shown high sensitivity. Nevertheless, MOS sensors have poor selectivity

because of the interference caused by other gas molecules and similar VOCs. Hence, a miniaturized sensing technology is desired to perform in-situ VOCs monitoring and provide specificity and accuracy. A convincing platform to accomplish real-time and accurate multi-VOCs identification utilizes the mid-IR spectrum. 21-23 Unlike VIS-NIR, mid-IR covers the unique absorption bands of the VOCs from λ = 2.5 to 8.0 µm. Mid-IR is capable of accurate and in-parallel identification of gas and liquid mixtures. 24-31 Hence, we developed mid-IR waveguide sensors to carry on real-time VOCs detection. Its detection mechanism was based on the evanescent wave sensing method. When analyte molecules approached the waveguide surface, the molecules absorbed the waveguide evanescent field, which consequently attenuated the waveguide mode intensity. Therefore, by measuring the spectral attenuation of the mid-IR waveguide mode, the compositions and the concentrations of the analytes can be resolved. Compared to GC, MOS, and VIS-NIR measurements, mid-IR waveguide sensing has the advantages of real-time monitoring, non-destructive detection, and high chemical specificity. The mid-IR waveguides consisted of As2Se3, a chalcogenide glass that is mid-IR transparent due to its low-phonon-energy. The As2Se3 waveguides were prepared by sputtering and lift-off processes, preventing the aggressive chemical etching or post thermal annealing required for solution processed As2Se3 thin films. The sputtered As2Se3 is an amorphous and robust material so it can be deposited on versatile substrates without the requirement of lattice matching

ACS Paragon Plus Environment

Analytical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 7

Figure 2. The structure of a 10 μm wide and 1.5 μm tall As2Se3 waveguide on 3 μm thick SiO2 undercladding captured by SEM from (a) the top and (b) cross-sectional view. The composition inspected by EDX mapping using As L-line and O K-line from (c, e) the top and (d, f) crosssectional views, respectively. Figure 1. (a) The schematic of the VOCs sensor that consisted of an As2Se3-on-SiO2 waveguide and a PDMS gas chamber. VOCs were injected and ejected through the chamber using the inlet and outlet tubes. The waveguide evanescent field was absorbed by the VOCs molecules attached to the waveguide surface. (b) The diagram of the VOCs measurement system. Mid-IR laser light was focused in a single mode fiber by a lens (RL) and delivered to the waveguide. The waveguide mode image and intensity were recorded by a camera placed after a BaF2 lens. VOCs samples were prepared by two mass flow controllers (MFCs) and a VOCs evaporation flask. MFC1 controlled the VOCs flow rate, and MFC2 regulated the diluting gas N2. Eventually, VOCs and N2 were combined into a gas tube and then injected into the PDMS chamber. (c) A microscope (MO) was utilized to reposition the fiber and the As2Se3 waveguide. The right of the sensor device was covered by a PDMS chamber.

or epitaxial growth condition. In addition, the As2Se3 sputtering process was conducted at room temperature, enabling its integration with other mid-IR materials. Since the sensing devices in this work were prepared by microelectronic fabrication processes, they are capable of integrating with present wireless microelectronics and can potentially be applied for remote VOCs detection.

Two VOCs, acetone and ethanol, were chosen to test the sensing accuracy of the waveguide. By comparing the spectral intensity change of the waveguide modes and the characteristic C-H absorptions, we were able to distinguish these two analytes. Furthermore, a response time < 5 s was achieved during VOCs detection. The fabricated mid-IR waveguide provided a small footprint sensing platform for non-destructive, real-time, and accurate VOCs detection. EXPERIMENTAL SECTION Device fabrication. Figure 1a shows the schematic structure of the mid-IR VOCs sensor. An As2Se3 ridge waveguide was created on a SiO2 under-cladding. Compared to the refractive index of SiO2, n = 1.45, As2Se3 has a relatively high n of 2.79. The large contrast in refractive index enabled the mid-IR wave to be confined inside the As2Se3 waveguide core. The As2Se3 waveguide was then covered by a polydimethylsiloxane (PDMS) chamber where the waveguide surface was exposed to the injected VOCs. The fabrication process for the As2Se3 waveguide is following: Using lithography, the negative tone photoresist NR9-3000PY was patterned on the 3 µm SiO2 cladding layer on top of the Si wafer. As2Se3 film was then deposited on the patterned substrate by RF sputtering a 99.99 % As2Se3 target with a power of 40 W. The waveguide was obtained after dissolving the photoresist and removing the excessive As2Se3. Since no etching

2 ACS Paragon Plus Environment

Page 3 of 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Analytical Chemistry

Figure 3. (a) The intensity profile of the waveguide mode simulated at λ = 3.4 - 3.7 µm. Ellipsoid intensity profiles were obtained in the As2Se3 waveguide. (b) The simulated intensity distributions in the z-direction, where the evanescent field expanded extensively at z > 1.5 µm containing VOCs.

process was utilized during the fabrication, the As2Se3 ridge waveguide showed a well-defined profile and smooth surfaces. Optical characterization system. A test station shown in Figure 1b was built to characterize the waveguide performance. The light from a 150 mW, nano-second pulsed laser was coupled into the waveguide through a reflective lens (RL) and a single mode fiber. The alignment between the fiber and the As2Se3 waveguide (Figure 1c) was controlled by a microscope. The gas delivery subsystem had two controllers to determine the concentration of the VOCs vapor in the carrier gas N2. The VOCs concentration was adjusting by tuning the ratio between these two flow rates. The gas sample was then delivered to a PDMS chamber placed above the sensor device, where the As2Se3 waveguides were exposed to the gas analytes. As shown in Figure 1c, the fiber was aligned with the front edge of the cleaved waveguide. The light emitted from the waveguide back facet was monitored by a mid-IR InSb camera. RESULTS AND DISCUSSION Morphology of the device. The morphology of the fabricated mid-IR sensor was first examined by scanning electron microscopy (SEM). Figure 2a indicates that the As2Se3 waveguide on the SiO2 under-cladding has sharp edges without deformation. From the side-view SEM image shown in Figure 2b, the waveguide structure has a flattened semielliptical profile with a 10 µm width and 1 µm thickness. The semi-elliptical structure was created by introducing a tilting

Figure 4. (a) The waveguide mode images captured at λ = 3.4 - 3.7 µm. Fundamental mode was clearly observed over a broad spectral range. (b) The 1-D intensity profile of the waveguide mode extrapolated along the y direction. This resolved Gaussian profile represented the fundamental mode. (c) Relative optical powers measured from waveguides of different lengths. The optical loss was 0.16 dB/cm by fitting the mode intensity attenuation at λ = 3.4 µm.

angle between the As2Se3 sputtering target and the substrate. Compared to a ridge waveguide, the semi-elliptical structure showed lower optical loss because it prevented the optical scattering caused by sharp waveguide edges. In addition, the waveguide facet was smooth and no bumps or indentations were found which is critical to minimize optical loss. The material composition of the waveguides was characterized by energy-dispersive X-ray spectroscopy (EDX) at the oxygen Kα and arsenic Lα lines. The mapping corresponding to the elements O and As revealed the profiles of the As2Se3 waveguides and the SiO2 under-cladding. Figure 2c and e are the EDX mappings captured above the device, and Figure 2d and f are the cross-sectional mappings. The structure of the As2Se3 waveguide and the SiO2 cladding were clearly resolved, and the waveguide height was determined to be 1 μm. The element mapping demonstrated that the grown As2Se3 thin film had a homogeneous



Page 4 of 7

Figure 5. The spectrum scanning of the waveguide mode. The images were recorded before and after the injection of the (a) acetone and (c) ethanol vapor. The absorption spectra of (b) acetone and (d) ethanol extrapolated from the mode intensity attenuation at different wavelengths.

composition along the surface and at different film depths. The high material homogeneity prevented optical loss caused by refractive index variations which are determined by the material composition. Optical simulation. The waveguide modes were numerically calculated over the spectrum by the 2-D finite difference method (FDM). The structure parameters applied in the simulation were defined based on the SEM images, where the semi-elliptical structure has a 10 µm width and 1 µm height. The refractive index for As2Se3 is 2.79 and SiO2 is 1.45. The light source is 12 × 8 μm, similar to the 9 μm core

fiber. Figure 3a displays the optical field of the waveguide mode calculated from λ = 3.40 to 3.70 µm. An elliptical mode was obtained in the waveguide center, and the evanescent field was observed on both the top (z ≥ 1.5 µm) and bottom (z ≤ 0 µm) of the As2Se3 layer. In addition, the evanescent fields become stronger at longer wavelengths. Figure 3b illustrates the 1-D intensity distribution simulated in the zdirection. A fundamental mode with a Gaussian intensity pattern was observed because As2Se3 has a large refractive index compared to that of SiO2. The sensitivity of the VOCs measurements was determined by the intensity of the evanescent fields. A transverse magnetic (TM) polarization was applied in this study because a stronger evanescent field


Page 5 of 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Analytical Chemistry was revealed along the z-direction than the y-direction due to the large y:z aspect ratio. Optical measurement. The optical performance of the As2Se3-on-SiO2 waveguide was characterized. Figure 4 displays the mode images and mode intensity attenuations measured at different waveguide lengths. In Figure 4a, a similar circular mode profile is observed between λ = 3.40 and 3.70 µm. No mode distortion was found indicating that the waveguides have a smooth surface and sharp boundary between the As2Se3 and the SiO2 layers. The efficient light wave guiding was attributed to the larger refractive index of As2Se3 than the SiO2. The 1-D mode intensity profiles were then extrapolated and are drawn in Figure 4b. A fundamental mode with a Gaussian profile was found between λ = 3.40 and 3.70 µm; the result was in agreement with the simulated mode profiles displayed in Figure 3. The mode intensity of waveguides with different lengths was measured to characterize the optical loss. A 0.16 dB/cm loss was found at the 3.50 µm wavelength by extrapolating the intensity change shown in Figure 4c. The loss is comparable to prior work.32-34 In addition, the loss of As2Se3 waveguide is lower than those of mid-IR Si waveguides of 0.7 dB/cm, AlN waveguides of 2.2 dB/cm, and Ge waveguides of 8 dB/cm.22,35,36 The resolved low optical loss indicates that the sputtered chalcogenide glass is highly transparent in mid-IR. The lowtemperature and non-etching fabrication process contributed to a smooth waveguide surface and sharp interface between the As2Se3 and SiO2 layers, minimizing the optical loss. Moreover, Rayleigh scattering is inversely proportional to λ4, so the loss due to the roughness of the surface decreases as the wavelength increases. Thus, the As2Se3 waveguides are an ideal platform for broadband mid-IR photonic circuits. Sensing tests of the device. Methanol and heptane were chosen to examine the waveguide sensing capability. The wavelength was continuously tuned between λ = 3.40 and 3.62 µm because this spectral range overlaps with characteristic absorption bands caused by the C-H functional group. Figure 5a shows the waveguide mode images and intensities recorded at discrete wavelengths as the acetone vapor was flown over the waveguide surface. A strong mode intensity was found between λ = 3.40 and 3.60 µm before any chemical was present. When acetone vapor was injected into the PDMS chamber and flown over the waveguide, the mode intensity sharply decreased at λ = 3.40 3.42 µm. Figure 5b is the absorption spectrum extrapolated from Figure 5a. The relative absorption intensity A was defined as (I0 - IF)/I0, where I0 and IF were the light intensities before and after the waveguide was exposed to VOCs vapor. The characteristic absorption associated with acetone was clearly observed at λ = 3.40 - 3.44 µm. On the other hand, when ethanol vapor was injected into the PDMS chamber, the mode intensity decayed over a broad spectrum at λ = 3.40 - 3.52 µm as shown in Figure 5c. From Figure 5d, the absorption band of ethanol was wider than that of acetone. Thus, the chalcogenide waveguide sensor was able to differentiate ethanol and acetone vapor by their distinct mid-IR

Figure 6. The in-situ VOCs detection was tested by measuring the waveguide intensity attenuation. a) The pulse duration of the ethanol vapor was set to 10 s. The mode intensity dropped instantaneously when the ethanol vapor was injected into the PDMS chamber. b) Ethanol gas concentration was changed from 100 % to 0 % by a step of 25 %. The mode intensity rapidly increased as the ethanol gas concentration decreased. c) The mode intensity measured at different ethanol concentrations. The waveguide mode intensity monotonically decreased as the ethanol concentration increased.

C-H absorption. This result agreed with previous Fourier Transform Infrared Spectroscopy (FTIR) measurements showing that the C-H absorption band from acetone was narrower in the mid-IR regime compared to ethanol. 38,39 To characterize the real-time sensing performance, the analyte was prepared by mixing the diluting gas N2 (99.999%)



with the ethanol vapor at different gas flow rates. Meanwhile, the laser wavelength was adjusted to the ethanol C-H absorption band at 3.46 μm, to continuously trace the ethanol concentration. A sequence of 10 s ethanol vapor pulses was injected into the PDMS chamber. Between the pulses, N2 was purged for another 10 s. As shown in Figure 6a, abrupt intensity attenuation was observed whenever the ethanol vapor was present and in contact with the waveguide sensor. Once N2 was purged into the chamber, the light intensity recovered to the original level. During the ethanol vapor monitoring, the fast response time < 5 s was attributed to the high sensitivity of mid-IR detection as well as the small gas chamber volume. To quantitatively correlate the mode intensity variation with the ethanol vapor concentration, ethanol vapor with concentrations of 0%, 25%, 50%, 75%, and 100% in N2 was sequentially injected into the PDMS chamber. As shown in Figure 6b, the light intensity decreased as the ethanol vapor concentration increased. By fitting the intensity and concentration plot, a monotonic dependence was observed and plotted in Figure 6c. This result demonstrated that the mid-IR waveguide sensor was able to accurately and continuously monitor the VOCs concentration. CONCLUSIONS Mid-IR As2Se3 waveguide sensors were demonstrated for non-destructive and real-time VOCs detection. The waveguides fabricated by microelectronic fabrication processes had smooth side walls and a sharp interface between the As2Se3 and SiO2 cladding layers. A clear circular waveguide mode with a small optical loss of 0.16 dB/cm was achieved. Two VOCs, acetone and ethanol, were applied to test the waveguide sensing performance. Strong mode intensity attenuation was found during acetone detection at λ = 3.40 3.42 µm and ethanol detection at λ = 3.40 - 3.50 µm. The spectral mode variation corresponded to the characteristic C-H absorption bands. Therefore, the waveguide sensor was capable of monitoring the VOCs concentration in-situ, providing a chip-scale sensor platform for remote and wearable VOCs detection.

AUTHOR INFORMATION Corresponding Author *[email protected]

ACKNOWLEDGEMENTS The authors appreciate the sponsorships offered by the Texas A&M University Presidential X-Grant and NSF-ERC PATHS-UP Program. The fabrication process and characterization of the devices were accomplished at AggieFab, the TAMU Materials Characterization Facility, and the Harvard University CNS.

REFERENCES (1) Adebesin, F.; Widhalm, J. R.; Boachon, B.; Lefèvre, F.; Pierman, B.; Lynch, J. H.; Alam, I.; Junqueira, B.; Benke, R.; Ray, S.; Porter,

Page 6 of 7

J. A.; Yanagisawa, M.; Wetzstein, H. Y.; Morgan, J. A.; Boutry, M.; Schuurink, R. C.; Dudareva, N. Science 2017, 356, 1386-1388. (2) Bari, M. A.; Kindzierski, W. B.; Wheeler, A. J.; Héroux, M.; Wallace, L. A. Build Environ 2015, 90, 114-124. (3) Hung, R.; Lee, S.; Bennett. J. W. Appl. Microbiol. Biotechnol. 2015, 99, 3395–3405. (4) He, Z.; Li, G.; Chen, J.; Huang, Y.; An, T.; Zhang. C. Environ. Int. 2015, 77, 85-94. (5) Taylor, S. M.; Sider, D.; Hampson, C.; Taylor, S. J.; Wilson, K.; Walter, S. D.; Eyles, J. D. Ecosyst. Health 1997, 3, 27–43. (6) Kampa, M.; Castanas, E. Environ. Pollut. 2008, 151, 362–367. (7) Bokowa, A.H. Chem. Eng. Trans. 2010, 23, 31–36. (8) Nurmatov, U. B.; Tagiyeva, N.; Semple, S.; Devereux, G.; Sheikh, A. Eur Respir Rev. 2015, 24, 92-101. (9) Huang, B.; Lei, C.; Wei, C.; Zeng. G. Environ. Int. 2014, 71, 118138. (10) Buljubasic, F.; Buchbauer. G. Flavour Fragr. J. 2015, 30, 525. (11) Alkhouri, N.; Cikach, F.; Eng, K.; Moses, J.; Patel, N.; Yan, C.; Hanouneh, I.; Grove, D.; Lopez, R.; Dweik, R. Eur J Gastroenterol Hepatol. 2014, 26, 82–87. (12) Filipiak, W.; Mochalski, P.; Filipiak, A.; Ager, C.; Cumeras, R.; Davis, C.; Agapiou, A.; Unterkofler, K.; Troppmair, J. Curr. Med. Chem. 2016, 23, 2112-2131. (13) Lin, P. T.; Lin, H. –Y. G.; Han, Z.; Jin, T.; Millender, R.; Kimerling, L. C.; Agarwal, A. Adv. Opt. Mater. 2016, 4, 1755-1759. (14) Sanchez, J. B.; Berger, F.; Fromm, M.; Nadal, M. H. Sens. Actuator B-Chem. 2006, 119, 227-233. (15) Lee C.; Chiang C.; Wang Y.; Ma R. Sens. Actuator B-Chem. 2007, 122, 503-510. (16) Rella R.; Spadavecchia J.; Manera M. G.; Capone S.; Taurino A.; Martino M. Sens. Actuator B-Chem. 2007, 127, 426-431. (17) Boeglin M. L.; Wessels D.; Henshel D. Environ Res 2006, 100, 242-254. (18) Huang J.; Wan Q. Sensors 2009, 9, 9903-9924. (19) Al-Hardan N. H.; Abdullah M. J.; Abdul A. A. Int J Hydrogen Energy 2010, 35, 4428-4434. (20) Al-Hardan, N.H.; Abdullah, M.J.; Abdul Aziz, A.; Ahmad, H.; Low, L.Y. Vacuum 2010, 85, 101-106. (21) Jin, T.; Zhou, J.; Wang, Z.; Gutierrez-Osuna, R.; Ahn, C.; Hwang, W.; Park, K.; Lin, P. T. Anal. Chem. 2018, 90, 4348-4353. (22) Jin, T.; Lin, H.-Y. G.; Lin, P. T. ACS Appl. Mater. Interfaces. 2017, 9, 42905–42911. (23) Jin, T.; Li, L.; Zhang, B.; Lin, H.-Y. G.; Wang, H.; Lin, P. T. ACS Appl. Mater. Interfaces. 2017, 9, 21848−21855. (24) Gattass, R. R.; Rhonehouse, D.; Gibson, D.; McClain, C. C.; Thapa, R.; Nguyen, V. Q.; Bayya, S. S.; Weiblen, R. J.; Menyuk, C. R.; Shaw, L. B.; Sanghera, J. S. Opt. Express, 2016, 24, 25697-25703. (25) Lin, P. T.; Jung, H.; Kimerling, L. C.; Agarwal, A.; Tang. H. X. Laser Photonics Rev. 2014, 8, 23–28. (26) Rodrigo, D.; Limaj, O.; Janner, D.; Etezadi, D.; Abajo, F. J. G.; Pruneri, V.; Altug, H. Science. 2015, 329, 165–168. (27) Singh, N.; Casas-Bedoya, A.; Hudson, D. D.; Read, A.; Mägi, E.; Eggleton, B. J. Opt. Lett. 2016, 41, 5776–5779. (28) Lochbaum, A.; Fedoryshyn, Y.; Dorodnyy, A.; Koch, U.; Hafner, C.; Leuthold, J. ACS Photonics. 2017, 4, 1371-1380. (29) Kumari, B.; Barh, A.; Varshney, R. K.; Pal, B. P. Sens. Actuator B-Chem. 2016, 236, 759–764. (30) Testa, G.; Persichetti, G.; Bernini, R. IEEE J. Sel. Top. Quantum Electron. 2018, 24, 5700108. (31) Gutierrez-Arroyo, A.; Baudet, E.; Bodiou, L.; Lemaitre, J.; Hardy, I.; Faijan, F.; Bureau, B.; Nazabal, V.; Charrier, J. Opt. Express. 2016, 24, 23109–23117. (32) Ma, P.; Choi, D.; Yu, Y.; Gai, X.; Yang, Z.; Debbarma, S.; Madden, S.; Luther-Davies, B. Optics Express 2013, 21, 29927-29937. (33) Ashok, N.; Lee, Y. L.; Shin, W. J. Jpn. J. Appl. Phys 2017, 56, 032501.


Page 7 of 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Analytical Chemistry (34) Carlie, N.; Musgraves, J. D.; Zdyrko, B.; Luzinov, I.; Hu, J.; Singh, V.; Agarwal, A.; Kimerling, L. C.; Canciamilla, A.; Morichetti, F.; Melloni, A.; Richardson, K. Opt. Express 2010, 18, 26728-26743. (35) Mashanovich, G. Z.; Milošević, M. M.; Nedeljkovic, M.; Owens, N.; Xiong, B., Teo, E. J., Hu, Y. Optics Express 2011, 19, 71127119. (36) Younis, U.; Luo, X.; Dong, B.; Huang, L.; Vanga, S. K.; Lim, A. E-. J.; Lo, P. G-. Q.; Lee, C.; Bettiol, A. A.; Ang, K-. W. J. Phys. Commun. 2018, 2, 045029. (37) Jadhav, D. L.; Karthick, N. K.; Kannan, P. P.; Shanmugam, R.; Elangovan, A.; Arivazhagan, G. J. Mol. Struct 2017, 1130, 497-502. (38) Plyler, E. K. J Res Natl Bur Stand 1952, 48, 281-286.

Table of Contents graphic


Mid-Infrared Chalcogenide Waveguides for Real-Time and Non

Recommend Documents