激光应用及光谱学 Laser Spectroscopy

Department of Electronic and Electrical Engineering

EE986 Assignment and Professional Studies

Group Project Interim Report

Name: Kuo Sun

Zhe Zhang

Nan Zhou

Content

Abstract (2)

1. Introduction (3)

2. Background (3)

2.1 Principle of LASER (3)

2.1.1 Deconstructing the LASER (3)

2.1.2 Underlying physics of LASER (4)

2.1.3 LASER Oscillation (4)

2.2 Principle of TDLS (5)

2.2.1 TDLS with Direct Detection (6)

2.2.2 TDLS with Wavelength Modulation Spectroscopy (6)

2.3 Fundamentals of Cavity Ring-down Spectroscopy (7)

2.3.1 Basic CRDS Set-Up (8)

2.3.2 Principle of CRDS (8)

2.3.3 Technical Characteristics of CRDS (9)

2.4 Principle of photoacoustic spectroscopy (9)

2.4.1 Foundational Principle (9)

2.4.2 Physical Process (10)

2.4.3 Advantages of Photoacoustic Spectroscopy (10)

3. Industrial Application (11)

3.1 Industry applications of TDLS (11)

3.2 Cavity Ring-Down Spectroscopy for Combustion Studies (12)

3.2.1 Experimental Set-up (12)

3.2.2 Methodology for CRD Flame Experiment (12)

4. Further work (14)

5. References (15)

Abstract

Modern spectroscopy which has the advantages of immunity to electromagnetic interference, resistance to chemical corrosion, high sensitivity, large bandwidth, and remote operation has become the preferred option for industrial gas monitoring.

This paper presents the basic principle of laser operation which involved to the spectroscopy discuss in the next section. Then the paper discusses the fundamental of three different types of spectroscopy--Tunable Diode Laser Spectroscopy, Cavity Ring-down Spectroscopy and Photo acoustic Spectroscopy. Furthermore, the applications in industrial of the spectroscopy mentioned before are given to provide a further explanation. Finally, the future work is shown to make the project plan clear.

1.Introduction

The title of this group project is ‘Optical Fibre Gas Sensors’. Gas sensing has been an important issue since the existence of mankind. This project involves a number of optical gas sensing techniques especially different kinds of spectroscopy and how each technique can be used in industrial applications. In the project each member will mainly do the research on one specific kind of spectroscopy and study the knowledge of its industry applications. Under the permit conditions an experimental system will be used to measure the characteristics of spectroscopy.

2.Background

2.1 Principle of LASER

LASER, which is the short name for Light Amplification by Stimulated Emission of Radiation, has already explained its main process in the full name.

2.1.1 Deconstructing the LASER

As an optical oscillator, a laser can be deconstructed into three essential elements —pump, gain medium and resonator. Figure 1 below could show the detailed structure of a laser.

Figure 1: Structure of a laser [1]

Pump acts as source of energy, providing external energy to gain medium, allowing it to amplify light. Generally, it can be specified into different types of optical pump, thermal pump, electrical pump and chemical pump. The types utilized should be determined by gain medium.