(Projfk IRPA 02-07-040-017)

APPLICATIONS OF LASERS AND ELECTRO-OPTICS

B.C. Tan, K.S. Lqw. Y.H. Chen, Harith Ahmad and T.Y. Tou,Institut Pcngajian Tinggi,

Univcrsiti Malaya,59KM) Kuala Lumpur, Malaysia.

ABSTRACT

Supported by the IRPA Programme on Laser Technology and Applications, many types of lasershave been designed, constructed and applied in various areas of science, medicine and industries.Amongst these lasers constructed were high power carbon dioxide lasers, rare gas halide excimcrlasers, solid state Neodymium-YAG lasers, nitrogen lasers, flashlamp pumped dye lasers and nitro-gen and excimer laser pumped dye lasers. These lasers and the associated electro-optics system,some with computer controlled, are designed and developed for the following areas of applications:

1. Industrial applications of high power carbon dioxide lasers for making of i.e. components andother materials processing purposes. Prototype operational systems have been developed.

2. Medical applications of lasers for cancer treatment using the technique of photodynamictherapy. A new and more effective treatment protocol has been proposed.

3. Agricultural applications of laser:, in palm oil and palm fruit- fluorescence diagnostic studies.Fruit ripeness signature has been developed and palm oil oxidation level were investigated.

4. Development of atmospheric pollution monitoring systems using laser lidar techniques.Laboratory scale systems were developed.

5. Other applications of lasers including laser holographic and interferometric methods *"»• <h-non destructive tcsline of materials.

The activities of the group (from 1988-1990) have resulted in the submission of a patent for a laserdevice, publication of many research paper sin local and overseas journals and conference proceed-inns, completion of 1 Ph. 11. dissertation and 6 M.Phil theses. Currently (1991), a toial of 3 Ph.D., f>M.I'hil research programmes aie involved in this research and development programme.

(Projck IPJ'A 02-07-04-017)

TEKNOLOGI DAN PENGGUNAAN LASER DANELEKTRO-OPT1K

B.C. Tan, K.'.lpw. Y.H. Chen, Harith Ahmad and T.Y. Tou,Institut Pcngajian Tinggi,

Universiti Malaya,S9100 Kuala Lumpur, Malaysia.

ABSTRAK

Untuk Program IRPA (Pcrindustrian) ke alas Laser Teknologi dan Penggunaannya, berbagai-bagaijenis laser iclah direkabentukkan dan dipcrgunakan dalam pelbagai bidang sepcrti sains, perubatandan pcrindi! .irian. Dianiara laser-laser yang dibina adalah laser karbon dioksida (cnaga tinggi, lasereksimcr gas nadir halida, laser keadaan pepejal Neodymium-YAG, laser nitrogen, laser pencelupyang dipam olch lampu suluh, laser pcncclup yang dipam oleh laser nitrogen dan eksimer. Laser-laser lersebui dan juga rangkaian siste.ii elcktro-optik, ada yang dikawal oleh kompuler, adalahdircka dan dikembangkan untuk penggunaan dalam bidang sepcrti dibawah:

1. Penggunaan perindustrian dengan laser karbon dioksida tenaga tinggi untuk menandakomponcn i.e. dan Iain-lain tujuan pemprosesan banan-bahan. Sistcm 'prototype' ini telahdikembangkan.

2. Pcnugunaan pcrubatan bagi laser unluk rawatan barah dengan menggunakan teknik terapilulodinamik. Satu prolokol baru yang lebih berkesan untuk rawatan batah lelah dicadangkan

3. Punggunaan pcrlanian bagi laser dengan kacoah pengesanan fluorosens minyak kelapa sawn(i.m huah-buahan kclapa sawit. Kacdah penandaan kemasakan scsuatu huah dan lakar ktnk--.iiijjn minyak kclapa sawit teljh disiasjtkan.

4. Pcrkcmbangan sistcm pengukuran pencemarar ::da;a dengan menggunakan teknik laserlid.ir Sistcm-siitcm makmai tclah dikembangkan.

5. Ljm-Lun penygunaan laser termasuk laser holografi dan interferomctri unluk ujian bahan-Kih.in Ijnpa-kcmu.snahan (Non-DcslruilivL1 Testing).

Akimli-.iklmli kumpuldii ini (1'AS.S-llWO) iclah mcnuhasilkan penycrahan satu paten imtuk scbuah-ii.it l.iscr. |v ncriiaan t).m\jk kcrtas-kcrja pcnvclulikan di dalam jurnal-jurnai (empatan dan luarnciicri d.ui JL'UJ djlam pcrsidanpan dan simposiuiu. pcnyclcsaian 1 discrtasi Ph.D. (Doktor Falsalah)d.m <> (CMS i M.l'liil) Sarjana Falsafah. Pada mjsa mi (1991), scjumlah 3 Ph.D.. '> M.Phil programI'i iiu Iklik.in tfl.ih icrlihjl dalam pcnyclidikan tlan porkembanuan program ini

1. INTRODUCTION

Under the Laser and Electro-Optics Technology and Applications Programme, advanced laserbased methods and instrumentations have being developed for use in industries, medicine, agricul-ture, remote sensing and a few other areas. The development of such process controls and methodsare essential as MaJaysia strives to become technologically advanced.

Thus, in the development of such laser based instrumentations, many useful laser systems have beendesigned and developed. These range from the low power nitrogen gas discharge lasers for palm oilfluorescence studies to high power transverse electric excitation (TEA) carbon dioxide lasers forintegrated circuit components marking. Other types of lasers such as the solid state and liquid dyelasers have also been designed and constructed. During this process of laser development, manyimportant associated technologies in high voltage techniques, electronic switching methods, highvacuum techniques and the usage of optoelectronic devices have also been developed.

Amongst the applications of these lasers, the efficient marking of ic components using high powercarbon dioxide lasers have been developed. Such laser markers are finding increasing usage in theelectronics industry as alternative automated processing technique. Lasers are also used for materi-aJs processing including non-destructive testing (NDT) methods for metal fatiquc and fault analysis.For medical applications, a new and more effective procedure for cancer therapy has been proposedby the group. Rapid diagnostic methods have also been developed for palm fruit ripeness and palmoil oxidation level studies. Remote sensing methods for the measurement of atmospheric pollutionhave also been developed.

This paper outlines the progress achieved in the design and development of such lasers and theapplication of these lasers and electrooptic systems for tiuterent purposes. A perspective on theongoing programme currently supported by the IRPA programme is also presented

2. LASER BASED APPLICATION SYSTEMS AND INSTRUMENTATION

for a laser based application system to be functional, many advanced instrumentation and tech-niques have to be developed. A schematic layout of the major components required lor laser basedapplication system is shown in Fig. 1. This consists firstly of a laser system with its associated hiuh

LaserLaser J Interactionbeam | of light

* ! with

Scatteredlight v

5pectr.ilfilter

tor i

Kit;. 1 Schematic diagram ol a typical laser instruiniiitaliiiii

voltage and switching modules together with its vacuum system and optical cavity. The laser outputis then directed and/or focussed to a target chamber where the specimen to be processed is placedfor a specific laser light and materials interaction. The resulting scattering signals are then spectrallyfiltered and detected using appropriate photon detection system. The signals are then digitised andprocessed using on-line data acquisiton devices. Normally, an inexpensive and fairly powerful PCmicrocomputer system is used as the controller to ensure the integrated operation of the entireelectro-optical system based on a laser for a specific application.

The development with respect to the different components of such a system and its applications arcdetailed further in the following sections.

2.1 DESIGN AND CONSTRUCTION OF LASER SYSTEMS

Many different types of lasers have been designed and developed. These included both gas dis-charge lasers, solid state lasers and liquid dye lasers.

• Table 1 summarises the types of lasers constructed thus far. The development of these lasers arefurther described in the following sections.

Table 1 List of Lasers Designated and Constructed

Laser

1. N 2

2. TEA-COj

3. Xe-CI

4. He-N-,

5. CW-CO-,

Design Type

Low pressure,Blumlein discharge

UV preiomsed

small cavity

UV presior.iscd

High pressure,2 stage Marx

Long!:udir..il. !nw pressure

Output

l - 5 m J5 - 10 ns. pulse

4 J/pulse

300 mJ/pulse

60 mJ, 10 ns

337 nm - 4 mJ42S nm • 1 mJ

HI W

Reference

..2.3

4

5.(>

7

0 MetalVapour

i Transverse :!•;".

CuBr. 5 Mi.-, .small volume

j Gold, srn.'.l; MilumcI

3 w

) mW

Oyc Lasers

! FlushLmp ' Cnxf.j i , K«' • 1 Jpumped Oyc laser i

2- N-> laser pumped j Osciiia;»i .n.";>in'ier 5(Xi uJd \ i laser j simuiuru-.i.;.. •lvj.il wavelength

- Solid-S<:ilr

'i S^i V.iJ i C.'oinp.iv MI-, ' < j -swi l t hc.l i n j . IUn>

: V.I ,-:J

(1) Nitrogen Lasers

Nitrogen lasers are gas discharge lasers and are the simplest and the most inexpensive lasersto be constructed. These nitrogen lasers have, however, found many applications in differentareas of science and industries. Fig. 2(a) shows a schematic diagram of a nitrogen laser.Basically, it consists of a high voltage supply source charging up an energy storage capacitor,C . On the switching of the spark gap device (S.G.), a rapid high current pulse is driven acrossthe laser channel which when appropriately arranged will give rise to the stimulated emissionof amplified radiation, i.e. a laser pulse. A cross section of a simple nitrogen laser driven by afast Blumlein discharge circuit is shown in Fig. 2(b) [1].

)

i—

)

/A -

^—i\ \

• p

r c

SP

=-

T r y

LE

Laser cr.an.-iel Mylar shoe;

Fig. 2 Schematic diagram of: (a) the circuit diagram and (b) a nitrogen I;ISIT (11

The output of a nitrogen toscr is ni)rm.)lly j short Ij.scr pulse of 5-10 njimsccnnd (ns) longwith peak powers up to a megawatt (MW). The high UV output power ol .i1 nitrogen lasermakes it a useful laser source tor the excitation of fluorescence as well .is in pumping liquiddye lasers. Four nitrogen lasers of different sizes and different power specifications havebeen designed and constructed jnd are used for different areas ol spettroscopy includingpalm fruit ripeness and palm oil oxidation level analyses |2] and pollution monitoring |1.3|

(2) TfcA Carbon Dioxide Lasers

Over the past few years, three different designs of a transverse excitation atmospheric (TEACO2 lasers have been designed and constructed with laser output which ranged from 300 m.to 4J [4,5,6]. Fig. 3 shows the schematic of the 4-Joule TEA-CO2 laser system [4] whiclemploys profiled and nickel-plated electrodes. Two rows of small of capacitors arc mountecalong both sides of the laset channel. During switching of the spark gap, high voltage sparl

. - across the gaps between these capacitors which produces UV radiation for preioaizing thelasing gas medium. The formation of arcs allow the small capacitors to be charged by thedumping of the storage capacitor which eventually discharge across the laser channel whenthe laser-channel impedance is lowered sufficiently by the UV-preionisation.

These CC>2 lasers arc very efficient, typically more than 10% efficient in converting fromelectrical to optical energy, have very high energy output. These laser output when focussedwill produce the electri jl breakdown in air to form sparks. When appropriately masked andfocussed, these lasers will produce permanent markings on plastics and form the basis for theindustrial marking of IC components [4]. These lasers have also been used for the annealingof amorphous silicon semiconductor materials as a technique for the processing of efficientsolar cell fabriation [6].

high voliage

..ii'c- ground

£"3 in

Fig. 3 End-on view of a high power TEA-CO2 laser system [4|

Lxcimer Laser-XeCI

A class of high-power UV lasers known as the excimer lasers have found important applica-tions in the electronics industry for photolithography in i.e. manufacturing These rare-caslulidc lasers have also found many other applications in .science and industries. However,these lasers are technologically more demanding than those ol a mtroecn laser and are moreexpensive to construct.

An exomer laser with xenon and chlorine gases forming the cxcimei laser medium njs re-cently constructed |7J. The laser delivered about 60 milhjeule (mj) nl laser enerey in aboutlu us ol pulse width with a output power of 6 MW peak. This laser, (".-sides the verv hiehdischarge current requirement, also requires the design ot an ellicieni preiomscr system to

obtain uniform discharge inside ihc laser cavity. As shown in Fig. 4, two rows of the capaci-tors are attached along the laser channel. One of them forms the UV-prcionizc,r when high-voltage arcs are produced between the upper and lower capacitors. The other row of capaci-tors is used as (he main damping capacitor for fast laser-channel discharge.

I Ins laser [7| has been used for pumpiog dual-wavelength dye laser for atmospheric studies.Oilier applications of the laser are being explored.

Secondary Capacitor

SVC Water Pic--

rig. 4 Sectional view of a XeCI excimer laser 17]

(4) Hash lamp Pumped Dye Lasers

Some llashlamp pumped dye lasers have been designed and constructed. The flashlamps ireh.isK.iiiy high-voltage discharge tube operat ing at reduced pressure of air which arc thenjir.im-L-d according to geometrical optics as to efficiently excite the liquid J ic medium. Hi- 5sh->u.s .1 coaxial ftashlamp pumped dye [<H| which have been operating with rhod.iminc dyes asa laM;i.; medium. The yellow output of the laser was designed for potcnli.il application in thelas,.-! :iihoiripsv of kidney stone. The power and frequency of the laser is K-iru: improved lor

I - •;

S i . . [ i i . i i . i l \ii-v» MI I i i ; i - . i i l . i t n p | i i l l i i | j t i l i lvr I . I M I | S |

Metal Vapour Lasers

Since 1989, we have embarked on developing metal vapour lasers. A Copper Bromide |9j anda Gold Metal Vapour [10] lasers slarled operating after a year of design and constructionwhich included high-voltage resonant clurger and high frequency triggering unit for EEVceramic-sealed hydrogen thyratron. Up to date, the copper bromide laser could only giveabout 10 watt of output at about 6 kHz of operating frequency and less than 1 % of efficiency.This means that an optimization program would be necessary in order to increase its output.This laser is intended for use for laser lithotripsy and other industrial applications.

On the other hand, the gold metal vapour laser gi"cs up to a maximum of 300 raW of outputfor a short cavity length of 40 cm. It is expected to yield more than 1 W of output at 632.8 nmwith a i m long cavity tube. Fig. 6 shows the schematic of a coaxial laser system which arecommon to both designs of the copper bromide and gold metal vapour lasers. The goldvapour laser is intended for use for the cancer therapy program.

laserchannel

Capacitor C?

Capacitor C2

ig. 6 Schematic diagram for a coaxial metal (copper bromide or gold) vapour laser [9,10]

((>) Solid State Neodymium Doped Glass and YACi Lasers

Nd-VAG and glass lasers have found many applications in industries, science and medicinedue to its simplicity in operation and reliability. A hiuh power Nd-glass laser with 4 J oulpulhas been designed and developed |11). Tow compact Nd-YAG lasers (12.13) have also beendeveloped for various laser pulse modulation, O-switching dnd modclockine studies. These.infrared lasers have also been used for frequency conversion using non-linear 0plic.1l m.ilcri-als. The miniature (matchbox size) Nd-YAG laser was used lor prototype laser ranuc hndinustudies |12|. Pit*. 7 shows J diagram of a compact N<J-Y-\f > l.iser CIinstructed.

Helium-Nitrnyrn l-iser

1 h i s i s j n e x t e n s i o n in t h e d e v e l o p m e n t o l n i i ro i -v . n I . I M T S v \ i o p t I v m o u t p u t p u l s e - , . i r e i i h

( . l i n e d M i m i l t j i i c o u s l v T h i s l a s e r r e q u i r e s n i u c . ^ . ':u-Jier <.n.ir.-im- - . . i l t . m c j n J .1 i w u s i . t e c \ 1 . » \

c e n e r j l o r h,\~. b e e n d e s i g n e d . U p t o A n i J . i l d . j . i i ' A . I \ .•:. • : i l - : : : l . i s e r n u t p i i t i s o h t . i n n - . l l i u

| ) i : l s c \* 'nl(h ul j h o u l 4 r ^ T h i s l a s e r is i n t e r . O e i i ->u :-..- ::i [ ^ ' H i l u t n n i o n i l o r i P L ' p r o r r . n n -A

si i i . i i l m ^ u h l i i u s i / e NiJ > A ( r w a s d e s i g n e d :r\ :•. ;i ii 1. -1 : • . : : ; : • . ' : i ! i i : iU! e x p e n m e n i | I<

2J..1 m

Fig. 7 Schematic diagram of a compact Nd-YAC laser [12]

(S) Continuous Wave (CW) Carbon Dioxide Lasers

A prototype high power carbon dioxide laser for material processing of wddiny, cutting andmetal heat treatment purposes have been designed and constructed. This work lias beenbased on an earlier studies of a lower power laser system which has yielded insufficientenergy (10 W) for materials processing [15). The prototype laser is a transverse discharge,transverse gas flow system instead of the longitudinal discharge configuration of ilic smallerlaser system. Various parametric studies have been conducted on the prototype system. Oncecompleted, a scaled up 1 kilowatt laser system suitable for various precision metalurgicalapplications will be developed.

: 1)1.\ Kl.Ol'MKNT OK LASKK-HASKI) AI'I'MCVI IONS

) 1 l l l I l l N f I ' J j l l A | I | > I I O I ( I ( I M H o f l , l l . N C I ' . t

A |>• i i i n i v | i r 1 1 i K 1 1 | m w c i T I ' i A ' C i i l i n i i i l i n x i i l c I . i M • i l i . i v l u ' i ' i i i l r v c l < > | M ' i l i • >• i l u l i i

I - I I - I t i i m i r s c i m i | ) i i n c u t s i n I ' J H H | l | . A . s j i n p l c n l , i i n . i i k i - i l p L i s l i i - i i1 . < • i r i i | i < n n - n i r • . h . . u n n

I 11.1.. S . I ' l i i 1 I , i s c I i i i . i i k r r s y s t e m l i a s s i n c e l i c c n i i | i ) ' . i . n l i - i l I n I n 1 i . i p . i l i l c n l I I I M - I ^ I I U M H I m ' l i

1 1 ' i >t* I i 11 v t" i i | i i ' l . i l i n i l . V . M u m s l U ' s i f ' l l U M I I U I ' S h . t v r i n - c n i i i i j i i n v n t . 1 i n l l i r . \ . i i m I M l>.

> 1 1 ' L ' I . I t I i ) I I . i I . i s a I . I N C I m . i i k e r ( i n t h e c l e c l i o i i K ' . s i i u l u s i i y , , i i m - i l i . m u ' . i l I r r i l t - i • . v . i n n l u . i

I n l u - i l c v i ' l i i p r c l .

I i n . H \ s : u n p l c o f a L i s c r m ; i r k c t l p l a . s i i c i . i \ c o r n p i i n t r n t H I

At ihe same time, the design and development of a prototype high power CW-CO2 laser forcutting and welding of materials has been carried oul. A low power device has been in opera-tion but has too low power for industrial applications. The construction of the high powerunit has been completed and the operating characteristics of this laser system has been inves-tigated. A number of design features have been modified and adapted to achieve the neces-sary threshold bsisg conditions. This laser system has been designed for ihe culling andwelding of materials.

2) Medical Applications of Lasers

The group has made significant advances in the field of pnotodynamic therapy (PDT) ofcancer using lasers (16,17,18]. Besides the development of laser devices for cancer therapy,the group has proposed a new protocol of immediate PDT which has been proven (o be atleast 5 times more effective, in terms of the dosage of the drug needed and the response totreatment obtained, when compared to the conventional protocol currently practised. Fig. 9shows a comparison of the results obtained using the new protocol as compared to that ob-tained using the conventionally praticed protocol. Clinical trials using this new procedure ofcancer treatment will be conducted using drugs prepared at the Clean Room constructed. Aprovisional licence to manufacture the drug at the University of Malaya has been obtained.

120

100

TUMOUR RESPONSE TOIMMEDIATE AND DELAYED PDT

~80t- -.

£ [C.

v ? 1

//

- : ' --]

IMMEDIATEPOT

-I— i

5 0 >0 0 :•_• 0DOS&GE Of MpO lm(.-tfl

ZOO

Fig. 9 A comparison of the tumuur response to the immediate PDT and the delayed PDT (IS)

The group is also involved in the development of various laser systems for medical •';';!:' ••tions. A more efficient metal vapour laser system [10] has been successfully developed ,'orcancer treatment. A patent [19| on a laser liiiht delivery system for cancer trcalmcni li.i-. .>'••.•<being submillcd hy members of the group

J) Agricultural Appiicaduns of Lasers

Using a nitrogen laser njnslructcd. a microcompiiicf controlled laser induced Ilimn--.. •system has been dc\clnr>cd lor the processine nl p.ii,-n Iruil ripeness | 2 | JS well as for p.ii'voxidation level dclcit ion [20\ Since must c r c jn i t materials lluoresccs strongly ur.vier !)•

power UV laser light, such laser induced fluorescence technique has been developed toprovide a remote sensing method of extracting information on palm fruit ripeness and palmoil oxidation level arising from shipping and storage. Fig. 10 shows a schematic arrangementof a laser induced fluorescence system and some results obtained for palm oil related studies.

Since a large amount of data will have to be gathered for routine and rapid processing pur-poses, il is needed that faster data acquisition procedures be developed. An optical multi-channel analyser system for rapid data acquisition and processing has been developed.

n

CRUDE PALM OIL

610 6*0Wavelength (nm)

• '̂ - H)ui) Experimental set-up for laser induced fluorescence of palm nil using nitrogen laser.(l>) \ characteristic fluorescence spectra of crude palm oil. (2.20)

•*) Pollution Studies Using Lasers •

Light Detection .ind Ranging (LIDAR) techniques have been developed for (ha detection olitj>.c poiluijnt concentrations in the atmosphere to less than 10 parts-pcr-billion (ppb) [1.7|.ThiN ii bjscd on ihe lechnique of simultaneous dual wavclenmh from single dye laser whichHJI r>cen developed lor monitoring of ambient NO2 concentration to less than 10 ppb (parts-per-fiiiionj j 1]. A new type of much higher power laser, a UV excimer laser, has also beendeveloped lo enjhlc higher power operation of the lidar system as well as for detection olSO2 and o/onc |~]

Other optical and laser techniques for the measurement of atmospheric pollution have alsobeen developed. These included optical differential absorption spectrophotometer [21] basedon ha'ogen lamps as light source as well as using Mie scattering methods for the measure-ment of atmospheric visibility accurately.

r-'ig. 11 shows a schematic of the experimental setup of a simultaneous dual channel spectro-photomctric detection system Jar ground based monitoring of atmospheric pollutants.

Laser outout\sOutput oirror

:' r 1 r. ', •: r

.-1 c r o -c c c p u c e r

Fig. 11 Schematic diagram of dual wavelength laser Jidar system [1,7]

5) Lasers for Non-Destructive Testing of Materials

Work has been conducted for the NDT speckle interferomctric studies of materials [22].Non-destructive tesing of materials such as rubber tyres and metal fatiques due to cithermechanical or thermal stresses can be performed rapidly and reliably using laser interfero-melric techniques. Such interfcrometric methods have been conducted using digital imaginglor rapid data acquisition and processing. Applications to industrial processes and monitoringare being conducted.

V ... k has also been conducted on the investigations of crystal damages due to light irradia-

4 M MMAKV OK PROGRESS ACHIEVED

i Air the period I98S to 1990, the group has achieved significant progress in the devclnpmeni ofMM.:\ .ind in I he applications of these laser systems in diverse areas of interest The croup haddi .. inped mjny types of lasers |24| for various applications, ranging from iruliisln.il. medical, aizn-<.iiiiui.il. in\ irunmentj | nuiniloring, materials processing etc. Some of the Ijsi-rs jrc ne;ir mjrketu-Ih^ -I .ii UN. 1 lie group had also made significant contribution in the licld oi u n c cr treatment usirn;I.IS».II tiy |u<ipusing a more effective pholodvnamic treatment procedure u h u h has shown better. IIDI.-III iLs|hinsc to trejlmunt than previously nbljined Clintrai triaK vnll v»-,Mn , n I'I-II

jfNii.ii.irv is now a recogm.sed center oi excellence in iBc ftcld <>l Livrr- J».I -k <.1ro-<>r>lies Four:: j.:..m: prmif.ims (3 weeks each, in I9S4. I'J.\(). \')SH and one TWO) on 1J-J ••• j n j •kctr-voptics re-SCJI^II were conducted by the group for physicists from the developing countries js well as from

Malaysia, funded by UNESCO and other international agencies. The laboratory has also conducteda 6-month training program for the United Nations University for physicists from the developingcountries in the field of laser research in 1986.

1'KR.SPLCTIVE

While some progress has been made in laser research at the University of Malaya, it is noted thatthe emphasis in the first ten years have been biased towards the development of different types oflaser systems as technological development. However, in the last few years, with the availability ofmore advanced instrumentations, various studies of a more detailed nature have been initiated.Thus, time resolved spectroscopy of laser initiated sparks in different materials as well as basiciomsation processes in gas discharges are being initiated. In parallel with these are the furtherdevelopment of applications of lasers in various areas of medicine, agriculture and induslriai applica-

As an important by-product of this program, the research group has been actively involved in thetraining of higher degree candidates and technical manpower. A list of the Ph.D. and M.Phil, gradu-ates is shown in Table 2. These graduates are now contributing actively in the further developmentof these laser and electro-optic technology either in other local institution of higher learning or inlocal research institutions or in the private industrial sector. The research program continues tosupport the training of other higher degree candidates. A list of the current research projects under-taken is shown in Table 3.

Table 2 List of higher degrees (Ph.D. and M.Phil.) completed between 1988-1990

Ph.D. Dissertation Theses Titles and Supervisors

1. M. Olivo(1990)

M.l'hit. Theses

C.K. Lee(19SS)

S J. Tan(198S)

S C. Tanr/y.sv;

K.H. Won;.'

MJ. /.,,imJ

Photodynamic Cancer Therapy: Development of a simplelight source and investigation of an alternative treatmentprocedure'.(Supervisors: K.S. Low, B.C. Tan and L.M. Looi)

Theses Tides and Supervisors

'Differential optical absorption spearometry for measurementof atmospheric pollution'.(Supervisors: -'.. j . Low, [i.C. Tan and L.M. Looi)

'Investigation of a high power TEA-CO2 laser for markingpurposes'.(Supervisors: K.S. Low. B.C. Tan and Y.H. Chen)

'Fabrication and cluiractcnzution of a coaxial dye laser for thestudy of llie photothennal effect'.(Supervisors: B.C. Tan, C.S. Wony and K.S. Low)

'Laser induced fluorescence studies of organic materials'.(Supervisors: K S. IJ>W, |i C Tan and Y.H. Chen)

'Investigation ofWinTet luin mm -labelled haemaioporphvnnderivatives for nuc^a' 'nmrir^ of malignancies'.(Supervisors: M ! •, iviihv, K S Low and N 11. Tan)

'Inivitigattun uf u < nmp.it : .'.'•/• YA(i Uiu-r fur Ivjit i/.-fi'i : / ' " i

(Supcivisciis KS Ui«* li .\IIIIKU1 ami H C T.m)

1 ;

Table 3 List of current higher degrees programs (1991)

Ph

1.

2.

3.

M.r

I.

2.

3.

4.

5.

6.

D. Programs

C.K-Ang

K.H. Wong

Y.A.Tan

>hii Programs

K.H. Chong

K.H. Cheah

M.L. Liew

K.C. Tee

W.S. Scow

K.F. Lee

Project Titles and Supervisors

Speckle fnlerferometry for Non-Destructive Testings of Materials(Supervised by B.C. Tan and Y.H. Chen)

Wong Kali Hieng • Time resolved spcaroscopy of complexionisation products produced by high power lasers.(Supervised by K.S. Low and B.C. Tan)

Laser spectroscopy of palm oil related materials.(Supervised by K.S. Low)

Project Titles and Supervisors

Dual wavelength He-N2 lasers for pollution monitoring.(Supervised by K.S. Low and B.C. Tan)

Cold vapour lasers for cancer therapy.(Supervised by K.S. Low and B.C. tan)

Copper bromide lasers for medical applications.(Supervised by K.S. Low and B.C. Tan)

Two phase fluid flow studies using lasers.(Supervised C.F. Than and K.S. Low)

X-ray productions using high power lasers.(Supervised K.S. Low and T.Y. Tou)

Non linear optical studies using solid state lasers.(Supervised by H. Ahmad and K.S. \JI\V)

ACKNOWLEDGEMENTS

This work was supported in part by the University of Malaya (Insdlul Pcngajian Tinggi) EquipmentVote and Malaysian MPKSN-IRPA vote 02/17/12.

It is noted that this multi-disciplinary research programs imolvcs many areas of applications in dif-ferent disciplines. Specialist input from researchers from ihe Faculty of Medicine and F.nginoi-rini;have been included in some of these research projects on J p'"iect hj.sis. Their active collaborutinnsand contributions are acknowlcdued.

REFERENCES

[1] Tan, C.H. and Low, K.S., Proc. 3rd Tropical College on Applied Phys., Kuala Lumpur,1988, p524-531.

(2] Wong, K.H., 'Laser induced fluorescence studies of organic materials', M.Phil. Thesis,University of Malaya, 1988.

[3| Tan, C.H., 'A differential absorption lidar system based on a tunable dye laser', Ph.D.Thesis, University of Malaya, 1988.

|4j Tan, SJ. and Low, K.S., J. Fiz. Mai. 9, 15 (1988).Also, Tan, SJ., 'Investigation of a high power TELA-CO^ laser for marking purposes', M.PhilThesis, University of Malaya, 1988.

[5] Ang, C.K., Tan, S.J. and Low, K.S., Proc. 3rd Tropical College on Applied Phys., KualaLumpur, 1988, p44S-454.Also, Ang, C.K., 'Investigation of uv-preionised atmospheric pressure gas laser', M.Sc.Thesis, University of Malaya, 1988.

|(J] Poh, L.K., Chen, Y.H., Tan, B.C., 'Propagation of melt front in an amorphous silicon filmirradiated by a dye laser", Nat. Physics Symp., June, 1989, IFM publication, p218.Also, Poh, L.K., Ph.D. Thesis, University of Malaya, 1990.

(7) Lau, S.L. and Low, K.S., Proc. National Phys. Symp., Kuala Lumpur,Also, Lau, S.L., 'Studies of atmospheric pollution propagation and dispersion', Ph.D.Thesis, University of Malaya (submitted, 1991).

[SJ Rasiah, I. and Tan, B.C., Proc. 4th Tropical College on Applied Physics, 1990 ( to bepublished).

|'J) Liew, M.L., M.Phil. Thesis (in preparation), University of Malaya.

(l ' l | Cheah, K.E., M.Phil. Thesis (in preparation), University of Malaya. ;

[11] Ahmad, H., 'OpticalAmplifier', Nal. Physics Symp., 1989, IFM Puhlicaiiim. p l W .

[ 1 - | Cliec, O.C. and Low, K.S , I ' r n 3rd Tropical College on Applied t'h\-. . Ku.ila Lumpur,I'W.S, p442-447.

Also , C h e e , O.C. , 'li'vestigiiiiiin nj a compact Nd-YAG laser for ln;lil i/i i. . :nw unit mn^ini;',

M.Phil. Thesis , Universily, M J I . I \ . I . V)H'l

| 1 3 | Ahmad , H., 'Nd-glass luser' (unpubl ished) .

[ M | Chong, K.U., M.Phil. Thesis (in preparat ion) , University of M.il.u.i

I'.^l 1'oh, L.K. and Chen, Y II., f'r... 2nd Tropical College on Applied I'll-, N KiVil . i |Lumpur,[1353-366.

1.5

[16| Low, K.S. and Olivo, M., Invited Lcclurc on 'Review of recent progress of photodynamictherapy of cancer', Proc. International Workshop on Lasers and Applications, Indorc,India, November, 11>X) (to be published by Wiley-Eastern Publ. Co.).

(I7j Zainuddin, J., Olivo, M., Baskaran, G., Paramsothy, M. ar.d Low, K.S., 'Efficacy ofWm-Tc-labellcd lipd for imaging and therapy of neoplastic tissues', Abst. World Congresson Medical Physics, San Antonio, November, 1989.Also, Zainuddin, J., 'Investigation of .99m Technetium-labelled haematoporphyrin deriva-tives for nuclear imaging of malignancies', M.Phil. Thesis, University of Malaya, 1989.

| IS] Olivo, M., Low, K.S., Looi, L..M. and Tan, B.C., 'Investigation of immediate photodynamictherapy for cancer treatment', Mcd. Sci. Res., 1989, 17, 31.Also, Olivo, M., 'Photodynamic cancer therapy: development of a simple light source andinvestigation of an alternative treatment procedure', Ph.D. Thesis, University of Malaya,

119] Low, K.S. and Tan, B.C., 'A laser device for cancer treatment' (patent submitted, 1989.

|20] Yeoh, K.H., 'Laser induced fluorescence studies of palm oil oxidation level', M.Sc. Thesis,University of Malaya (under preparation).

(21) Lee, C.K., 'Differential optical absorption spectrometry for measurement of atmosphericpollution', M.Phil. Thesis, University of MaJaya, 1988.

|22] Ganesat, A.R., Ang, C.K., Sirohi, R.S. and Tan, B.C., 'Low light illumination digitalspeckle pattern interferometry', 4th Asia Pacific Physics Conf., SeouL August, 1990.

(23| Santbiran, N., Radbakrishua, S. and Tan, B.C., 'Laser radiation damage in cesium bromidecrystals', 4th Asia Pacific Physics Conf., Seoul, August, 1990.

[24) Low, K.S. and Tou, T.Y., Invited Lecture on 'Development of lasers and application sat theUniversity of Malaya', Proc International Workshop on Lasers and Applications, Indoro.India, November, 1990 (to be published by Wiley-Eastern I uhl. Co.).