dr. kathleen richardson - asp · 2020-05-28 · exploiting intrinsic material properties for...

Dr. Kathleen Richardson

Current Research Activities

HMO and ChG bulk glass/fiber for MIR applicationsCrystallization kinetics in MIR (Tellurite) glassesHigh Raman gain glasses – fibersExtrusion behavior of micro‐structured fibers

(NSF‐MWN, Universities of Bordeaux, Limoges and Torino, University of Adelaide)

Glasses for Precision Glass MoldingFundamental studies of glass‐mold interactionsCompositional engineering of glass workpiece and mold surface chemistry/microstructureModeling of workpiece material response via FEA

Final size/shapeStress relaxation measurements and modeling

(ARO, Edmund Optics, SCHOTT glass)Novel chalcogenide glass (ChG) bulk, films and fibers

Undoped and doped (NP and QD) ChG materials for magneto‐optic and active applications ChG metamaterials: device design and fabrication

(NSF, Raytheon and AFRL in collaboration with Penn St.)Chalcogenide glassy films for planar chemical sensors

(DTRA and DoE – NA‐22 in collaboration with MIT, Delaware)

Exploiting intrinsic material properties for improved integrated chalcogenide

waveguide resonators for mid‐IR sensingProf. Kathleen Richardson

J. Wilkinson, S. Novak, J. D. Musgraves, N. Carlie, B. Zdyrko, I. LuzinovSchool of Materials Science and Engineering, Clemson University

V. Singh, A. Agarwal, L. C. KimerlingMicro‐Photonics Center, Department of Materials Science and Engineering

Massachusetts Institute of TechnologyJ. J. Hu

Department of Materials Science and EngineeringUniversity of Delaware

A. Canciamilla, F. Morichetti, A. MelloniDipartimento di Elettronica e Informazione, Politecnico di Milano, Italy

Glass and Optical Materials Division MeetingPaper GOMD‐SIII‐035‐11

Glass Processing and Characterization Laboratory

Acknowledgments

Glass Processing and Characterization Laboratory 10

US Dept. of Energy (DoE) under contracts# DE‐SC52‐06NA27341 and DE‐NA000421DTRA under contract # HDTRA1‐10‐1‐0073

NSF – Materials World Network (MWN) program DMR‐0807016LasINOF program – Agence Nationale de la Recherche ANR (grant # ANR‐05‐BLAN‐0212‐01)

NSF INTL REU grant ENG‐0649230 & IGERT EEC‐0244109

Ongoing collaboration: Norm Anheier, Amy Qiao, Brad Johnson, John McCloy, Brian RileyPacific Northwest National Laboratory (PNNL)

Outline


• Motivation – Sensing and chalcogenide glass (ChG) materials• Material selection, processing, manufacturing and applications

– Infrared spectroscopy– Chemical and biological molecular detection– Precision glass metrology

• Leveraging materials attributes to solve key device limitations– Loss reduction – thermal reflow

• Exploiting the glass’ low Tg– Loss reduction and compositional optimization – solution based glass processing

• Exploiting selective chemical durability– Device performance optimzation

• Exploiting photosensitivity• Future efforts

• MIR device integration via composition tailoring, and (hybrid) solution processing strategies

• enhancing device sensitivity via PTS (FOM optimization: dn/dT)“Integrated chalcogenide waveguide resonators for mid‐IR sensing: Leveraging material properties to meet fabrication challenges,” N. Carlie, J.D. Musgraves, B. Zdyrko, I. Luzinov, J. Hu, V. Singh, A. Agarwal, L. C. Kimerling, A. Canciamilla, F.

Morichetti, A. Melloni, and K. Richardson Optics Express 18 25 (2010) 26728‐26743

Glass Processing and Characterization Laboratory 12

Cl

F

At

Br

I

Ar

Ne

Rn

Kr

Xe

P

N

Bi

As

Sb

S

O

Po

Se

Te

He

Al

B

Tl

Ga

In

Si

C

Pb

Ge

Sn

Compositional development: Chalcogenide Glasses (ChGs)

Bulk Glass (Target) Preparation

SiO2

ZBLAN (Fluoride)

Ge‐Sb‐S/Se/Te

As‐Te‐I Te‐I

Composition dependent properties‐Refractive index: 2‐3Thermal stability: Tg ~ 100‐500 °CAbsorption band gap: 500‐2000 nmIR cut‐off: 10 ‐20 μm

Planar chem‐bio sensors for MIR work are based on As‐Ge‐Sb‐S‐Se system


Wide transparency windows make ChGsideal for biological & chemical sensing

Visible NIR Mid‐IR Far‐IRUV

m)

S=OO‐HO‐H

water transparency

N‐O N‐O

C‐H fingerprint region

functional group region

silicasilicon

chalcogenidesheavy‐metal oxides

germanium


Material choices for planar ChG sensors

Planar devices based on thin films tend to undergo more rapid cooling compared to bulk materials during deposition

MUST have understanding of bulk/film property differences (refractive index, dispersion, dn/dT, chemical stability and compatibility)

Linear and nonlinear properties (low TPA)Low optical loss (dB’s/m) ‐ purificationHigh index contrast compact devices

MUST be compatible with deposition and further back‐end fab process for complex device layouts

system compatibility, preferential material response and interaction, functionalization with ChG compatible polymers

KNOWN photo response – thermal and optical stability during fabrication and post‐fab

Need to measure refractive index in spectral range of use to ±0.001 GOAL: low loss, HIC, CMOS‐compatible ChG film optimized for MIR spectral window (MIR)

Schematic of a second order filter made by two directly coupled micro‐ring

resonators

CO2laser

QCL

IR He‐Ne

Vis. He‐Ne (632.8 nm)

Fiber laser

Interchangeable detectors• Ge photodiode (Vis‐NIR) • un‐cooled MCZT

GaP prismZnSe 2.5:1 telescope Ge window

2kHz chopper

• Four (4) lasers added and aligned collinear to reference He-Ne using an IR camera• Tunable CO2 waveguide laser: 9.2 – 10.6 μm• Maxion distributed feedback (DFB) quantum cascade laser (QCL): 5.348 μm• IR HeNe gas laser: 3.391 μm• Agilent Telecom DFB fiber laser 1.547 μm

• HeCdZnTe IR detector added: Vigo Systems, Model PVM-10.6 un-cooled due to tight workspace low SNR due to thermal background. IR lasers chopped at 2kHz, signal recovery with current preamp. and lock-in amplifier Modified detector mount allows placement near prism surface (<1mm) for expanded scan angle range

•SiO2/Rutile prisms replaced by GaP/Ge• Transmission from 0.6 to 20 μm• Better index match to chalcogenide glasses (ChG)• Refractive index of prism was calibrated against ZnSe primary reference material

• Sample/prism heater added to stabilize temperature • High dn/dT of IR prism materials (4x10-4 for Ge) is significant compared to instrument resolution

PNNL Metricon for MIR/LWIR index measurement (2009)

PNNL Modified Prism Coupler(2011)

16

-N. Carlie, et al., Rev. Sci. Inst., 82 5 (2011) 053102-A. Qiao et al., Proc. SPIE 8016-13 (2011)

Available Prisms

wavelength(µm)

Ge Prism (40o)

Si Prism (55o)

GaP Prism (50o)

Rutile Prism (60o)

GGG Prism (50o)

high low High low High low high low high low

0.6328 2.90 2.01 2.69 1.95 1.84 1.00

1.547 3.14 2.32 2.70 1.81 2.54 1.80 1.81 1.00

3.391 3.14 2.12 3.10 2.28 2.68 1.78 2.54 1.79 1.79 1.00

5.348 3.14 2.11 3.09 2.28 2.67 1.77 2.54 1.79 1.75 1.00

10.591 3.13 2.11 2.63 1.73

11.5 3.13 2.11 2.61 1.71Transparency*

(µm) 1.8-17 1.2-10 0.6-13 0.45-5.7 0.36-6.0

dn/dt* (ppm/oC) 400 150 130 -95 20

17

The current measurement accuracy is ±1x10‐3 and is expected to improve to ±1x10‐4 after obtaining calibration standards and implementing thermal control of the prism and the measured samples.

18

Mid‐IR ChG Characterization

C1 As(36) Sb(6) S(58)

C2 As(42) S(58)

C3 As(36) Ge(6) S(58)

C4 Ge(23) Sb(7) S(70)

15,5

16,0

16,5

2,1

2,2

2,3

2,4

2,5

C1 C2 C3 C4

mol

ar v

olum

e (c

m3/

mol

)

refr

activ

e in

dex

refractive index at 5.3 ummolar volume

2,02,12,22,32,42,52,62,7

0 2 4 6 8 10 12

refra

ctiv

e in

dex

wavelength (µm)

Clemson bulk glass dn/dC1C2C3C4

Vm=M/ρ

Bulk – film propertiesAs2Se3 glass


0 2 4 6 8 10 12

2.66

2.68

2.70

2.72

2.74

2.76

2.78

2.80

2.82

2.84

2.86

2.88

Ref

ract

ive

inde

x

Wavelength (m)

Bulk glass As-deposited film Annealed film (170oC - 3hrs)

Other key data:‐Material dn/dT (system capability to 200°C)‐Optical homogeneity (to ±1x10-4 )

Mid-IR metrology tools include a Twyyman-Green interferometer (bulk optics), amodified Metricon prism coupler (thinfilms), and a custom waveguide lossmeasurement system (waveguides andfibers)

Planar integration: key to miniaturization, mass production, and cost & power consumptionreduction

Source, resonator, detector,signal read-out & processingcircuitry, fluidic system …

The OLD way:discrete devices

Planar integration

The NEW way:integrated chips

Smaller, better cheaper & greener

Waveguide integrated detector (Si‐Ge, PbSe/PbTe)

Compact and robust device structure Evanescent coupling efficiency > 90% Reduced dark noise and improved SNR

Molecular imprinted artificial antibody

Combined chemical & geometrical recognition for high specificity Superior durability and robustness compared to their natural counterparts

Ultra‐high‐Q resonator sensorDoped glass ring laser

Monolithic structure on Si Co‐planar coupling with low‐loss glass waveguides

Atomically smooth surface for reduced scattering loss Enhanced photon‐molecule interaction for high sensitivity

CMOS circuitry

Microfluidic channel

Source

DetectorMicrofluidicchannel

CMOS circuitry

22

Surface‐functionalized ‘lab‐on‐chip’ optical sensor systems

• IR transparency for detection of absorption signatures• High refractive index for small feature sizes• Low optical loss for high sensitivity resonators• Amenable to surface functionalization for selectivity

• Stable in chemical environment to be sensed• Able to be fabricated into waveguides/resonators

Glass for this application must be/have:

Two sensing regimes

Refractive index sensing

Shift of resonant wavelength

Absorption feature sensing

Decrease of effective transparency

As2S3: a model system for studying structural modificationsGe23Sb7S70: a stable glass ideal for sensing applications

As2S3 Ge23Sb7S70

Refractive index @ 1550 nm 2.37 – 2.42 2.15 – 2.33

Glass transition temperature 210 ºC 310 ºC

Stability against oxidation in an ambient environment

Blanket film: ok Patterned film: poor Excellent

• Film deposition– Thermal evaporation– Pulsed laser deposition– Magnetron sputtering– Spin‐coating

• Device fabrication– Waveguide– Bragg gratings– Photonic crystal

• Device integration

R. P. Wang et al., J. Appl. Phys. 100, 063524 (2006)

V. Ushanov et al., Semicond. Sci. Technol. 19, 787 (2004)**S. Song, et al., J. Non. Cryst. Sol. 355 (2009) 2272‐2278

N. Hô et al., Opt. Lett. 31, 1860 (2006)

M. Lee et al., Opt. Express 15, 1277 (2007)

**A. Saliminia et al., J. Opt. Soc. Am. B 17, 1343 (2000)

** all loss data is for unpurified bulk glass materials: < ~5 dB/cm @ 1550nm

**T.V. Galstian, et al., J. of Lightwave Technol., 15 8 1343 (1997)

B. Eggleton et al., Nature Photonics, 5 (2011) 141‐148

Requirement Material choicesSubstrate Large area (low cost), good mechanical properties

(robustness)Si, glass or metal acceptable: Si is

preferable for ease of integration other electronic and photonic devices on-chip

Under cladding

Excellent transparency at working wavelength, process compatibility, sufficient thickness (prevent

optical leakage)

Silicon oxide (for biosensing-NIR applications), ChG glasses (for chemical

sensing for NIR, MIR and LWIR)Buried bus waveguide

Index matching with resonator material, good optical transparency in wavelength range of choice

Silicon nitride, ChG glasses

Resonator Excellent transparency at working wavelength, preferably good chemical stability, amenable to

sidewall smoothing process (including reflow & solvent treatment), low photosensitivity & small or no aging

(for index sensing), possibility of athermal design (for index sensing), relatively high refractive index (> 1.8)

ChG glasses or other high-index glasses

Surface coating

Specificity, sensitivity enhancement without compromising optical loss or environmental stability

(Artificial) antibodies, polymers

Gas/liquid channels

Mechanical robustness, good chemical stability, process compatibility with WGs, wettability with liquid (in particular for sensing in an aqueous environment), biocompatibility (for certain biosensing applications)

Glass, polymer (e.g. PDMS, SU8)

Substrate

Under claddingBuried bus WG

Gas/liquid channel

Selective surface coating –functionalized polymer Resonator

Glass resonators are fabricated on silicon via a CMOS‐backend compatible lift‐off process

Lift‐off process flow

Resist coating

Development

UV exposure on a 500 nm i‐line stepper

Glass thermal evaporation

Lift‐off

Single‐source evaporation

Target heaters

Bulk glasses

Silicon substrate

~10-7 Torr

Tantalum boats

Ge23Sb7S70/As2S3

“Si‐CMOS‐compatible lift‐off fabrication of low‐loss planar chalcogenide waveguides,” Optics Express 15, 11798 (2007)

Wafer‐scale, parallel process Leverage on standard silicon‐

CMOS tools Non‐composition specific

As2S3Microdisk

Optical resonators can enhance photon‐matter interactions by orders of magnitude

Resonator

Light

Enhanced optical fieldEnhanced optical field

Long optical path lengthLong optical path lengthDetection limit: 0.02 cm‐1

Corresponding to ppmlevel sensitivity

and 3x more sensitive!

Further optimization: use of purified raw materials, enhanced resonator device designs and materials for ultra‐low loss components, is ongoing

Goal: surpass ppb sensitivity with superb selectivity to mixed streams withoutpre‐concentration

High‐Q ChG resonator sensor is capable of detecting refractive index (RI) changes as small as 8× 10‐7

Refractive index limit of detection 8× 10‐7 RIU (Refractive Index Unit) Demonstrated 10x improvement over commercial SPR sensors ! An additional 10x improvement expected by changing wavelength to near‐

infrared (e.g. 1.06 m) to minimize water absorption

RI sensitivity: 182 nm/RIU

Solution index increase

“Planar waveguide‐coupled, high‐index‐contrast, high‐Q resonators in chalcogenide glass for sensing,” Opt. Lett. 33, 2500‐2502 (2008)

= 1550 nm

The strong photon‐matter interactionin integrated high‐Q optical resonatorsmake them ideal for rapid sensing

Detection of refractive index change induced by surface binding of chemical orbiological molecular species:KEY ISSUES time constant of response to binding event, vapor/liquid analyteform, concentration of analyte within mixed stream of species

Specific surface binding

Low optical loss(High‐Q)

Strong molecule‐photon interaction

Sharp resonant peak & high sensitivity

“Design guidelines for optical resonator biochemical sensors,” J. Opt. Soc. Am. B. 26, 1032‐1041 (2009).

< 15 min

Objectives:Enhance evanescent wave sensor response to analyte of interest

Strategy:Create a polymer layer on top of chalcogenide glass waveguide with the ability to selectively bind analyte of interest

Approach:Grafting of a compatible polymer layer bearing chemical moieties able to react reversibly with the analyte

Polymer grafting

Analyte

ChG waveguide Change of the enrichment layerthickness and/or refractive index

Polymer coatings for chalcogenide glasses

Developing a selectivepolymer layer system

0 500 1000 1500 2000 2500 3000 35000.00

0.05

0.10

0.15

0.20

0.25

0.30

Time [s]

Hexane Acetone Chloroform Isopropanol Ethanol

0 500 1000 1500 2000 2500 3000 35000.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

Time [s]

Hexane Acetone Chloroform Isopropanol Ethanol

30

Per

cent

age

of th

ickn

ess

chan

ge

Detection by Infrared

• Spectra of analyte vapors in multi layer system have distinguishable peaks that can be used for detection.

3500 3000 2500 2000 1500 1000 500

0.000.01

0.000.020.04

0.00

0.01

0.00

0.01

0.000.010.02

Wavenumbers [cm-1]

Hexane

Acetic acid Abs

orba

nce

Ethanol

Isopropanol

Methanol

31

Signal strength by analyte flow and concentration

• Analyte is acetone, peak used is carbonyl b/w 1652‐1839cm‐1

• Signal strength increases with increasing flow rate.

20 to 80

50 to 50

70 to 30

100 to 0

0

0,2

0,4

0,6

0,8

1

1,2

1,4

Area

Multi‐layer concentration variable

10 to 1030 to 30 50 to 50

100 to 100

0

0,2

0,4

0,6

0,8

1

1,2

Area

Multi‐layer flow variable

• Analyte is acetone, peak used is carbonyl b/w 1652‐1839cm‐1

• Signal strength increases with increasing concentration.

32

Outline

• Motivation – Sensing and chalcogenide glass (ChG) materials• Material selection, processing, manufacturing and applications

– Infrared spectroscopy– Biological molecular detection– Precision glass metrology

• Leveraging materials attributes to solve key device limitations– Loss reduction – thermal reflow

• Exploiting the glass’ low Tg– Loss reduction and compositional optimization – solution based glass processing

• Exploiting selective chemical durability

– Device performance optimization • Exploiting photosensitivity

– Future efforts • MIR device integration via composition tailoring, and (hybrid) solution processing strategies • enhancing device sensitivity via PTS (FOM optimization: dn/dT)

“Integrated chalcogenide waveguide resonators for mid‐IR sensing: Leveraging material properties to meet fabrication challenges,” N. Carlie, et al., Optics Express 18 25 (2010) 26728‐26743

Thermal reflow successfully eliminates sidewall roughness and associated scattering loss: Ge‐Sb‐S

Viscous flow driven by surface tension removes roughness 50% optical loss reduction achieved via thermal reflow Magnitude of glass volatilization is small but measurable

“Optical loss reduction in HIC chalcogenide glass waveguides via thermal reflow,” J. Hu, N. Feng, A. Agarwal, L. Kimerling, N. Carlie, L. Petit and K. Richardson, Optics Express, 18 (2010) 1469–1478

35

Ground glass

Liquid solvent

Glass solution /Suspension

Optimization of glass‐solution spin‐coating conditions

Dissolution Spin‐coating Heat Treatment

Effect of: • Glass/solvent ratio• Dissolution time

On: • Film composition

Effect of: • Initial hold time• Spin speed • Spin time• Acceleration/Deceleration• Final hold time

On: •Film thickness•Uniformity/Coverage•RMS roughness

Effect of: • Soft‐bake time/temperature•Hard‐bake time/temperature

On: Refractive index Raman spectra (glass structure)IR spectra (residual solvent)

Three Stage Process

The following process variables were examined and optimized:

Goal: bulk composition = film composition

Goal: lowest roughness for highest thickness

Goal: film properties = bulk properties

Nathan Carlie, “A solution‐based approach to the fabrication of novel chalcogenide glass materials and structures,” PhD thesis, Clemson University (2010)

36

Infrared transparency of heat treated films

As42S58 derived from propylamine solution: 60°C ‐ 1hr soft‐bake + 90‐180°C – 1 hr hard‐bake

Solution derived films can be engineered for applications in infrared sensing

*Corrected for Fresnel loss

3 4 5 6 7 8 910

Wavelength (m)

4000 3500 3000 2500 2000 1500 1000

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Abso

rban

ce

Wavenumber (cm-1)

Propylamine 90 oC 120 oC 150 oC 180 oC

80 100 120 140 160 180

0.0

0.2

0.4

0.6

0.8

1.0

2900 cm-1

1600 cm-1

Abso

rban

ce

Heat Treatment Temperature (oC)

Absorption features near 2900 cm‐1 (N‐H) and 1600 cm‐1 (C‐N) decrease at higher temperatures.

N‐H bonds lost at a faster rate than C‐N bonds Probably through conversion of –NH2 to H2S

Absorbance near 3μm decreased 0.87 (90 °C) to 0.015 (180 °C) – (reduction of 98%)

37

Solution‐derived optical coatings Sources of optical loss: Typical solutions employed:

Roughness scattering is the dominant source of loss for most waveguide systems.

CU/MIT Provisional Patent issued

Material absorption Material purificationSubstrate leakage Geometry optimizationRoughness scattering Surface smoothing

AFM line‐scan along waveguide

• Waveguide RMS roughness reduced from 19 nm to 1.4 nm• Optical loss reduces by up to 50%• Cladding layer can be the same material as the waveguide

Index match to “sub‐layer/substrate”No adverse effect on the overall index profile

• Cladding layer can be different material (glass or hybrid coating)Allows creation of tailored or graded index profile

• Cladding layer is thin compared to waveguideMinimal effect on optical geometry/performanceSuitable for additional surface functionalization

Glass loading (mg/ml) / spin speed / Temperature

Waveguide surface cladding

Control of film thickness and quality with glass loading and water content

• Controlled by glass loading level, spin speed: target at = 3.4m, t =1m• Glass type (As‐S, GeSbS) does not have a noticeable effect on quality• Water content impacts quality; less of an effect on thickness (rms < 10 nm)

Amount of Glass in 10 mL of PA Spin Speed Thickness

0.2 g4000 rpm ~100‐150 nm

3000 rpm ~150 nm

0.5 g4000 rpm ~300‐350 nm

3000 rpm ~400‐450 nm

0.7 g

4000 rpm ~650‐700 nm

3000 rpm ~685‐715 nm

2500 rpm ~785‐815 nm

0.9 g4000 rpm ~800‐850 nm

3000 rpm ~830‐900 nm

Trimming of a coupled ring structure

Simulated transmission

In

Out

second order optical filter

flat‐top pass band…

R2

R1

Wavelength [nm]

Tran

smission

[dB]

1521.5 1522 1522.5 1523-20

-15

-10

-5

0 R2 R1

… provided that R2 R1

R2 ≠ R1

“Resonant cavity enhanced photosensitivity in As2S3 chalcogenide glass at 1550 nm telecommunication wavelength,” J. Hu, et al., Opt. Letters 35 6 (2010) 874‐876

Compensation of fabrication imperfections

Visible light trimming(halogen lamp)

Permanent compensation of fabrication imperfections

In

OutR1

nm .35012 RR

maskR2R1

Radius = 100 mFSR = 130 GHzBandwidth = 32.5 GHz

As2S3 double‐ring filter

Moving R1 only

light

R2

0.32 MW/cm2

Visible light trimming(microscope halogen lamp)

Trimming time ≈ 1 nm / 4 min

“Rigid” frequency shift of the filter response


Moving R1 and R2

Correction/adjustment of theworking wavelength


In

OutR1

mask

light

R2

0.32 MW/cm2

1520 1520.5 1521 1521.5 1522 1522.5

-20

-15

-10

-5

0


Photosensitivity relaxation

Wavelength [nm]

Tran

smission

[dB]

after 2° exposureafter 1 week

No relaxation effects

No bandwidth changes

After one week…


Top flatness preserved

In

OutR1

R2

• Shifting from NIR MIR ( – 3.25 m)– Device component geometries change

• Integration with source and detectors– Alignment– Packaging– New components and/or materials

• Isolators, lenses, filters

• New geometries of sensing regions to enhance further sensitivity– Photo‐thermal spectroscopy: exploiting dn/dT

Moving forward


Integration challenges

From C. Tsay, et al., “Chalcogenide glass waveguides integrated with quantumcascade lasers for on chip mid‐IR photonic circuits,” Opt. Lett. 35, 3324‐3326 (2010)

Further enhancing sensitivityPhotoThermal Spectroscopy (PTS)

Incident IR radiation Transmission

Medium

Scattering

Scatterers

Heat

Temperature change

Refractive index change

Key advantages:• Photothermal enhancement• Immunity to scattering interference

Spe

ctro

met

er

J. Hu, Opt. Express 18, 22174‐22186 (2010)

Cavity‐enhanced absorption

Cavity‐enhanced absorption

Resonator temperature

change

Resonator temperature

change

Resonant wavelength shift

Resonant wavelength shift

Localized heat generation

Light

Light circulation in cavity

Light Cavity

Simultaneous optical & thermal confinement in nano‐cavity PTS

Chipscale Optical Nano‐Cavity Enhanced Photo‐Thermal Spectroscopy (CONCEPTS)

PT enhancement factor > 104

Chalcogenide glasses (ChG) are ideal for nano‐cavity PTS

Material Refractive index

Thermal conductivity

(W/mK)

Thermo-optic coefficient (/K)

Figure-of-Merit (m/W)

ChG 2.81 0.22 1.4 × 10-4 /K 1.8 × 10-3

Silicon 3.45 149 2.3 × 10-4 /K 5.2 × 10-6

SiO2 1.45 1.38 1.0 × 10-5 /K 1.0 × 10-5

n: refractive indexα: thermo‐optic coefficient (dn/dT)σ: thermal conductivity

FOM n

J. Hu, “Ultra‐sensitive chemical vapor detection using micro‐cavity photothermal spectroscopy”, Opt. Express 18, 22174‐22186 (2010).

Goal: need precise material properties at wavelengths of interest/use

J. Hu, Opt. Express 18, 22174‐22186 (2010).

42 10~32

33 PQdVEGnnE

e Np

c Absorption cross‐section detection

limit: 10‐17 cm2 (a single molecule)

Potential of single, small molecule detection using chalcogenide glass nano‐cavities

• Chalcogenide glasses (ChGs) offer a blend of compositional‐tailoring opportunities and processing‐compatible strategies for optical components and devices for sensing in the MIR and LWIR.

• Traditionally considered “limitations” associated with ChG materials can be utilized to enhance component optical properties and device performance.

• Interfacing attributes of inorganic and organic materials and creative device designs can lead to novel glassy structures with unique functionality that will continue to enhance sensor specificity and selectivity to low ppb ppt levels.

Conclusions

dr. kathleen richardson - asp · 2020-05-28 · exploiting intrinsic material properties for...

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