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1.
Opt Express ; 28(23): 34279-34289, 2020 Nov 09.
Article in English | MEDLINE | ID: mdl-33182901

ABSTRACT

With an ever-increasing interest in secure and reliable free-space optical communication, upconversion detectors enabled through nonlinear optical processes are an attractive route to transmitting data as a mid-infrared signal. This spectral region is known to have a higher transmissivity through the atmosphere. In this work, we present an upconversion scheme for detection in the silicon absorption band using magnesium-oxide doped periodically poled lithium niobate to generate 21 mW of a 3.4 µm signal from commercial laser sources using a difference frequency generation process. Following a further nonlinear frequency conversion, via sum-frequency generation, the resulting signal at 809 nm is detected. We achieve >50 µW of signal and bit error rates of 10-7 from a single-pass nonlinear conversion for both the transmitter and receiver systems without the need for additional optical amplifiers at the receiving end. The error rates due to potentially reduced laser powers at the receiver end are investigated and laser noise transfer through our system is discussed.

2.
Biomed Opt Express ; 11(8): 4714-4722, 2020 Aug 01.
Article in English | MEDLINE | ID: mdl-32923073

ABSTRACT

Specific proteins and their aggregates form toxic amyloid plaques and neurofibrillary tangles in the brains of people suffering from neurodegenerative diseases such as Alzheimer's and Parkinson's. It is important to study these conformational changes to identify and differentiate these diseases at an early stage so that timely medication is provided to patients. Mid-infrared spectroscopy can be used to monitor these changes by studying the line-shapes and the relative absorbances of amide bands present in proteins. This work focusses on the spectroscopy of the protein, Bovine Serum Albumin as an exemplar, and its aggregates using germanium on silicon waveguides in the 1900-1000 cm-1 (5.3-10.0 µm) spectral region.

3.
Opt Express ; 28(15): 21382-21390, 2020 Jul 20.
Article in English | MEDLINE | ID: mdl-32752417

ABSTRACT

Periodically poled lithium niobate (PPLN) waveguides are a proven and popular means for efficient wavelength conversion. However, conventional PPLN waveguides typically have small mode field diameters (MFD) (≲6 µm) or significant insertion and/or propagation losses, limiting their ability to operate at multi-watt power levels. In this work we utilise zinc indiffused PPLN ridge waveguides that have a larger MFD, favourable pump/SHG modal overlap, and low insertion losses. Here for the first time, we have demonstrated continuous wave (CW) spectral narrowing from a PPLN waveguide, both with high efficiency and multi-watt second harmonic generation (SHG). 2.5 W of 780 nm has been produced by SHG of an amplified 1560 nm telecom laser with a device efficiency of 58% in a 4.0-cm long ridge waveguide. We have modelled conversion efficiency and applied experimentally measured waveguide parameters to show excellent agreement to the SHG spectra. Spectral narrowing of the full width half maximum (FWHM) of 35.7% has been measured as the nonlinear drive is increased. This work demonstrates that single-pass, multi-watt, CW SHG at 780 nm is feasible from our PPLN waveguide in the large conversion regime.

4.
Appl Opt ; 59(16): 4921-4926, 2020 Jun 01.
Article in English | MEDLINE | ID: mdl-32543488

ABSTRACT

We present the design and characterization of a zinc-indiffused periodically poled lithium-niobate ridge waveguide for second-harmonic generation of ∼390nm light from 780 nm. We use a newly developed, broadband near-infrared vertical external-cavity surface-emitting laser (VECSEL) to investigate the potential for lower-footprint nonlinear optical pump sources as an alternative to larger commercial laser systems. We demonstrate a VECSEL with an output power of 500 mW, containing an intracavity birefringent filter for spectral narrowing and wavelength selection. In this first demonstration of using a VECSEL to pump a nonlinear waveguide, we present the ability to generate 1 mW of ∼390nm light with further potential for increased efficiency and size reduction.

5.
Opt Express ; 27(17): 24538-24544, 2019 Aug 19.
Article in English | MEDLINE | ID: mdl-31510341

ABSTRACT

We have demonstrated the first MgO:PPLN ridge waveguides based on ZnO indiffusion and dicing. The fabrication process utilizes ductile regime dicing of a planar waveguide layer producing second harmonic generation (SHG) devices with a near-symmetric sinc2 spectral profile, indicating highly uniform 40 mm long devices. A near circular pump mode is also obtained enabling efficient coupling to single mode telecommunication fibers. A conversion efficiency of 145%/W, for 1560-780 nm SHG, has been measured.

6.
ACS Sens ; 4(7): 1749-1753, 2019 07 26.
Article in English | MEDLINE | ID: mdl-31264410

ABSTRACT

Protein sensing in biological fluids provides important information to diagnose many clinically relevant diseases. Mid-infrared (MIR) absorption spectroscopy of bovine serum albumin (BSA) is experimentally demonstrated on a germanium on silicon (GOS) waveguide in the 1900-1000 cm-1 (5.3-10.0 µm) region of the MIR. GOS waveguides were shown to guide light up to a wavelength of 12.9 µm. The waveguide absorption spectrum of water, showing molecular bending vibrations, was obtained experimentally and compared with a theoretical model showing good agreement. Measurement of a concentration series of BSA protein in phosphate buffered saline (PBS) from 0.1 mg/mL to 100 mg/mL was performed on the waveguide using filter paper as a flow strip, and the amide I, II, and III peaks were observed and quantified.


Subject(s)
Serum Albumin, Bovine/analysis , Animals , Cattle , Germanium/chemistry , Silicon/chemistry , Spectrophotometry, Infrared/methods
7.
Opt Lett ; 43(4): 791-794, 2018 Feb 15.
Article in English | MEDLINE | ID: mdl-29443995

ABSTRACT

This Letter demonstrates a refractometer in integrated optical fiber, a new optical platform that planarizes fiber using flame hydrolysis deposition (FHD). The unique advantage of the technology is survivability in harsh environments. The platform is mechanically robust, and can survive elevated temperatures approaching 1000°C and exposure to common solvents, including acetone, gasoline, and methanol. For the demonstrated refractometer, fabrication was achieved through wet etching an SMF-28 fiber to a diameter of 8 µm before FHD planarization. An external refractive index was monitored using fiber Bragg gratings (FBGs), written into the core of the planarized fiber. A direct comparison to alternative FBG refractometers is made, for which the developed platform is shown to have comparable sensitivity, with the added advantage of survivability in harsh environments.

8.
Opt Express ; 25(22): 27431-27441, 2017 Oct 30.
Article in English | MEDLINE | ID: mdl-29092216

ABSTRACT

We report transmission measurements of germanium on silicon waveguides in the 7.5-8.5 µm wavelength range, with a minimum propagation loss of 2.5 dB/cm at 7.575 µm. However, we find an unexpected strongly increasing loss at higher wavelengths, potential causes of which we discuss in detail. We also demonstrate the first germanium on silicon multimode interferometers operating in this range, as well as grating couplers optimized for measurement using a long wavelength infrared camera. Finally, we use an implementation of the "cut-back" method for loss measurements that allows simultaneous transmission measurement through multiple waveguides of different lengths, and we use dicing in the ductile regime for fast and reproducible high quality optical waveguide end-facet preparation.

9.
Opt Lett ; 40(9): 2016-9, 2015 May 01.
Article in English | MEDLINE | ID: mdl-25927772

ABSTRACT

We report the fabrication and characterization of high index contrast (Δn≈0.9) GeTe4 channel waveguides on ZnSe substrate for evanescent-field-based biosensing applications in the mid-IR spectral region. GeTe4 films were deposited by RF sputtering and characterized for their structure, composition, transparency, and dispersion. The lift-off technique was used to pattern the waveguide channels. Waveguiding from 2.5-3.7 and 6.4-7.5 µm was demonstrated, and mode intensity profile and estimated propagation losses are given for the 3.5 µm wavelength.


Subject(s)
Germanium , Infrared Rays , Optical Imaging/methods , Tellurium , Equipment Design , Optical Imaging/instrumentation , Optical Phenomena
10.
Opt Express ; 23(2): 1005-14, 2015 Jan 26.
Article in English | MEDLINE | ID: mdl-25835860

ABSTRACT

We demonstrate machining of precision slots in silica with nanoscale roughness for applications in photonics. Using our in-house developed milling system we have achieved machined slots with surface roughness of 3.0 nm (Sa) and 17 µm depth of cut. This result represents eight times improvement in surface roughness and forty times increase in depth of cut than previously reported. We also demonstrate integration of these milled slots with UV-written waveguides and Bragg gratings to create optical refractometers, based on monitoring Fabry-Pérot spectral fringe changes.

11.
Opt Express ; 22(26): 31801-13, 2014 Dec 29.
Article in English | MEDLINE | ID: mdl-25607148

ABSTRACT

A dual cantilever device has been demonstrated which can operate as a force sensor or variable attenuator. The device is fabricated using physical micromachining techniques that do not require cleanroom class facilities. The response of the device to mechanical actuation is measured, and shown to be well described by conventional fiber optic angular misalignment theory. The device has the potential to be utilized within integrated optical components for sensors or attenuators. An array of devices was fabricated with potential for parallel operation.


Subject(s)
Micro-Electrical-Mechanical Systems/instrumentation , Optical Devices , Silicon Dioxide/chemistry , Silicon/chemistry , Surface Plasmon Resonance/instrumentation , Transducers, Pressure , Equipment Design , Equipment Failure Analysis , Stress, Mechanical , Systems Integration
12.
Opt Express ; 19(13): 12462-8, 2011 Jun 20.
Article in English | MEDLINE | ID: mdl-21716485

ABSTRACT

A set of rapid prototyping techniques are combined to construct a laterally-tilted Bragg grating refractometer in a novel planar geometry. The tilted Bragg grating is fabricated in a silica-on-silicon planar substrate using a dual beam direct UV writing (DUW) technique. Lateral cladding mode confinement is subsequently achieved by physically micromachining two trenches either side of the direct UV written waveguide. The resulting device is demonstrated as an effective refractometer, displaying a comparable sensitivity to tilted Bragg gratings in a fiber optical geometry, but with the added advantages of planar integration.


Subject(s)
Microtechnology/instrumentation , Optics and Photonics/instrumentation , Refractometry/instrumentation , Ultraviolet Rays , Manufactured Materials , Microtechnology/methods , Models, Theoretical , Optics and Photonics/methods , Refractometry/methods , Silicon/chemistry , Silicon Dioxide/chemistry
13.
Opt Express ; 18(22): 23296-301, 2010 Oct 25.
Article in English | MEDLINE | ID: mdl-21164670

ABSTRACT

A new method for creating microcantilevers in glass allows integration of optical waveguides and Bragg gratings. Devices are fabricated by high precision sawing, followed by direct UV writing of waveguides with Bragg gratings and then chemical etching to release the freestanding glass structures. Optical measurement of the Bragg gratings together with piezo-actuation allows the mechanical resonances to be probed. By measuring the mechanical damping coefficient of the cantilever as a function of the gas pressure in a vacuum system the transition from the viscous to the molecular flow regime can be observed.

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