Project Overview Laser Spectroscopy Group A. A. Ruth Department of Physics, University College...

Project Overview

Laser Spectroscopy Group

http://laser-spectroscopy.ucc.ie

A. A. Ruth

Department of Physics, University College Cork, Cork, Ireland

(1) Optical trapping of spherical (droplet) particles (12 weeks)

(2) Establishment of a small weather station including the operation of a real-time wind shear LiDAR (6 weeks)

(3) Differential optical absorption spectroscopy (6 or 12 weeks)

(4) Laser induced breakdown spectroscopy (12 weeks)

Projects

Project 1

Optical trapping of spherical (droplet)

particles

Physical principle of optical trapping

Trap setup

Nebulizer

Trap chamber& illumination

Camera

Laser

M1

M2

M3

L1

L2

L3

BS

BS= beamsplitter

1064 nm

Objective lensBeamsplitter

Particle chamber

Mirror

Objectives

· Optically trap droplet or transparent spherical solid.

· Measure radius of trapped particles.

· Study the time the particle can be trapped for as a function of particle size and trapping parameters.

· Measure scattering from the droplet/particle and check whether whispering gallery modes were formed.

· Compare mode frequencies with expectation based on particle size. Project is for 12 weeks

Project 2

Establishment of a small weather station

including the operation of a real-time wind

shear LiDAR

Weather Station

• Temperature • Atmospheric pressure• Humidity• Precipitation• Wind speed• Wind direction

Standard parameters measured by a weather station:

Cup Anemometer

LiDAR Principle / Set-up

Telescope

Receiver Optics

Filters

Detector

(B)

Signal Processing

Data Acquisitio

n

Data Analysis

(C)

(A) Transmitter

(B) Receiver

(C) Data Processing

(A)

Laser

Beam Steerin

g

Beam Expander

Power Measurement

(A)

Transm

itte

r

(C)

Data

Pro

cess

ing

(B)

Rece

iver

(A) (B) (C)

Aerosol drifting with the wind.

Doppler shift of elastically backscattered lightused to determinewind speed and direction.

Wind (Doppler) LiDAR

Objectives

• Establish weather station.

• Deploy wind LiDAR.

• Implement wireless data transmission to a central hub.

• Analyse and interpret collected data.

Collaboration withCivil, Environmental & Energy Engineering Department(Dr. P. Leahy)

Project is for 6 weeks

Project 3

Differential Optical Absorption Spectroscopy (DOAS)

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Established method in trace gas detection:

Telescope

up to several kilometers

Lamp

Spectrometer

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Experiments in the project will take a little different approach.

Long-Path Differential Optical Absorption Spectroscopy

(LP-DOAS)

Different spectra

Steetlights of Cok observd during a merry knight after a kouple of white wine spritzerrrs.

Typical spectra of streetlights

http://1.bp.blogspot.com/-tFKtln8xlCo/UHkatCwW3oI/AAAAAAAABYo/g84HebxlXqw/s1600/led-street-lights2.jpg


Xe arc lamps ?



White LEDs ?


http://www.google.ie/imgres?imgurl=http://farm4.static.flickr.com/3576/3656251273_2bdc1085a1.jpg&imgrefurl=http://www.fastcompany.com/1299829/new-material-makes-white-led-home-lighting-pretty-certain&usg=__UsG_qzSjLoq9U0AOWXpHUyye9p0=&h=300&w=400&sz=101&hl=en&start=8&zoom=1&tbnid=tGD0xgnDP2h3DM:&tbnh=93&tbnw=124&ei=0GKBUPj-FYu4hAee-4DADw&prev=/images?q=pics+white+LED&hl=en&sa=X&rlz=1T4ADFA_enIE481IE481&tbm=isch&itbs=1

Typical spectra of streetlightsLow pressure Na lamp?


Typical spectra of streetlightsHigh pressure Na lamp?


http://www.google.ie/imgres?imgurl=http://image.tradevv.com/2008/06/25/yuanweibin_160248_600/high-pressure-sodium-lamp.jpg&imgrefurl=http://www.tradevv.com/chinasuppliers/yuanweibin_p_271f8/china-HIGH-PRESSURE-SODIUM-LAMP.html&usg=__jKo-p5cNw_el9srZhOPGmcsQDKw=&h=500&w=500&sz=17&hl=en&start=36&zoom=1&tbnid=GpjQkYGbm0zR3M:&tbnh=130&tbnw=130&ei=016BUKv1FM-4hAfu1YGIDg&prev=/images?q=sodium+lamp&start=20&hl=en&sa=N&rlz=1T4ADFA_enIE481IE481&tbm=isch&itbs=1

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Long path differential optical absorption spectroscopy

Telescope

street light

Spectrometer

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aerosol, dust, particulate matter

molecular and radical trace species

Molecules exhibit structured spectra Aerosol spectra have broad extinctionfeatures

Inte

nsity

I0

IaerIaer+Imol

l

Difference spectra are being evaluated !

Objectives

Characterize streetlight spectra and select the most appropriate ones for DOAS experiments.

Measure spectra during the entire night and evaluate long term stability of the setup.

Evaluate spectra and check whether (a) retrieval of aerosol extinction is possible,(b) retrieval of molecular absorption is possible,

notably of H2O or NO2.

Check feasibility for automized 2D-DOAS study over Cork.

Project can be offeredas 12 weeks or 6 weeks

Project 4

Laser induced breakdown spectroscopy

(LIBS)

High powerlaser pulse

computer

filter

spectrometer

lensshutter

Nd:YAG laser(doubled, 532 nm)

oscilloscope(power monitor)

CCD fibre

vacuumcell

Different gases: air, N2, O2, Ar

Laser Induced Breakdown Exp.

100 ns

400 ns

1000 ns

4000 ns

wavelength

log

(em

issi

on in

tens

ity)

Laser pulse duration typically 10 ns !!Focus typically >10000 K.


computer

filter

spectrometer

lensshutter



CCD fibre

vacuumcell

Naphthalene


oscilloscope

PMT

computer

filter

vacuumcell

HR mirror

GPIB

shutter





lens

Objectives

· Set up LIBS experiment.

· Measure “breakdown spectra” of air for different pressures.

· Measure “breakdown spectra” of other inert gases, e.g. He, Ar, CO2.

· Trap laser plasma emission in an optical cavity and interpret the results.

Project is designed for 12 weeks

Light source Detector

No sample

Conventional absorption spectroscopy

d Intensity I0

Absorbance (=optical density) A:

ln (I / I0) = d () = A

= absorption coefficient [cm-1], d = sample length [cm]

Light source.

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Detector

Absorbing sample (e.g. Gas)

Conventional absorption spectroscopy

d Intensity I

Project Overview Laser Spectroscopy Group A. A. Ruth Department of Physics, University College...

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