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"With the growth of optical communications using Low toss optical. fibers. the need for an optical switching system that exchanges optical. signals without any optoelectric and electro optic converter may arise. In this study, an experimental model of sliding prism switch using planar micro lens array has been constructed. The performance of the constructed switching device was studied by measuring insertion Loss. coupling efficiency and cross talk. The experiment shows that the measured results of insertion losses that is 6 and 7 dB are greater than the theoretically calculation that is 1.3 dB. The modulated signal has been measured as we t t ; the shape of the signal does not change after passing through the switch and on the other hand the amplitude of the output signal. is tower than the input signal due to the transmission Loss. I t is concluded that the experimental model of sliding prism demonstrate the potential application of planar micro lens in optical switch device."

"ABSTRACTLaser induced thin film production (LITFP) technique was employed for making plumbum (Pb) thin film by nitrogen laser deposition in miniature scale. The energy of nitrogen laser operated at 12.5 kv, 90 torr was 3.5 mj with 5 ns pulse duration, thus producing peak power at around 0.7 MW. Pb plasma of 1 cm diameter was generated in each laser bombardment, producing thin film above the glass substrate. The thin film characteristics were measured by means of their thickness and surface morphology using scanning electron microscope (SEM). It was proved that there was a linear relationship between the number of laser shots and film thickness."

"ABSTRAKRecently, the distributed index microlenses have been introduced as the novel elements for coupling device in microoptic circuitry. A potential advantage of such microlenses as microoptic components is the possibility of gaining a Large nemerical aperture so that incoming Light can be effectively guided, for example in optical coupler, branching circuits, wavelength multiplexer / demultiplexer and so on. The coupling property of microlenses is the basic application of microlenses in optical communication system. this study, a coupling circuit using paired microlenses with distributed index of refraction has been developed. The variation of coupling efficiency due to Lateral offset, angular misalignment and end separation of two coupled microlenses has been experimentally measured. Evaluation on the result was carried out by computer simulation based on phase space representation of ray tracing. It is concluded that the coupling property of distributed index microlenses is affected by the index profile of respective microlenses as predicted by phase space analysis. Furthermore the phase space representation has also been utilized to analyze the coupling efficiency of microoptical coupler."

"ABSTRACTIn spite of abundant experimental evidences supporting the viability of the laserinduced shock wave plasma model for the explanation of the important features oftheplasma and the associated spectroscopic characteristics, a controversy on the atomicexcitation mechanism in the plasma has remained to be completely resolved. In thisstudy the contributions of the shock wave model and two other most popular models,the electron-ion recombination model and thc electron collision model werethoroughly investigated. For that purpose, a special technique has been developed forthe direct detection of the charge current in conjunction with plasma emissionmeasurement dining the laser plasma generation and expansion. The current detectionwas performed by placing a partially transmitting metal mesh electrode at a distancein front of the sample surface with the sample target sewing as the counter electrode.The electric Held between the mesh and sample surface was set up and varied byapplying a variable DC voltage (0-400 Volt) between them. The laser plasma wasgenerated by a YAG laser (64 ml, 8 ns) tightly focused on a Cu target through themesh electrode in low-pressure surrounding gas. It was found that the charge currenttime profiles obtained at various gas pressures invariably exhibit a lack of consistentcorrelation with the emission time profile of the plasma throughout most of theemission period. The result of this study has thus practically eliminated anysignificant roles ofthe electron-ion recombination and electron collision models in theexcitation process. We are therefore led to conclude that the shock wave modelproposed earlier is most plausible for the consistent explanation of the secondaryplasma emission, while the other two models may have some contribution only at thevery initial stage ofthe secondary plasma generation.Key words: charge current, shock wave, electron-ion recombination and electroncollision.Praiseci is to the Lord for He is my reason in everything I do.This manuscript is never be done without the guidance by Pro£ Tjia May On, towhom I am extremely grateful. He also provided the support without which this thesiswould not possible. He is more than just a teacher for me for his words have deeplytouched me. Moreover, he also introduced me that knowledge is something we shouldshare among others and to improve the education in my country.I am also indebted to Prof. Kiichiro Kagawa at the Fukui University for providingthe atmosphere and the physical resources to make thesis writing in these times of fastpaced research. I am also thankful for the opportunity which is given to me to joinresearch together with him in his laboratory in Japan.Extra special thanks go to Dr. Hendrik Kurniawan for providing me withencouragement and support for this project. He is the first one who encouraged me totake Doctor Cotuse Program which seemed impossible at the beginning. Hiscompanion during research at Applied Spectroscopy Laboratory at University ofIndonesia is a leading experience in research for me.I am particularly grateful to the excellent team of referees who provided criticalcomments on this thesis. Their feedback was a great benefit to me.I gratefully acknowledge all my colleagues: Rinda Hedwig, Mangasi A.Marpaung, Hery Suyanto, MM. Suliyanti, Wahyu S. Budi, and Emon in AppliedSpectroscopy Laboratory at University of Indonesia, for their assistance and supportduring my study.My never-ending thanks to my beloved family, especially to my parents whoexhibited thoughtful patience over extended periods of time when I seemed to beinvisible. Thanks also to Loviana who helped me in all situations which I no longercan resist by myselflFinally, I apologize to all those who helped that I did not acknowledge specifically.I know there were many and greatly appreciate your assistance.August, 2002Author"

"A special interferometric technique with high sensitivity has been devised on the basis of rainbows refractometer without the use of an additional and delicate amplitude-splitting setup. This new technique was use for the characterization of shock wave plasma induced by a Q-sw Nd-YAG laser on various kinds of metal samples under reduced gas pressures. An unmistakable signal of density jump was detected simultaneously with the emission front signal. It is proved that at the initial stage of the secondary plasma expansion, the front of the emission and the front of the blast wave was coincide and move together with time. However, at a later stage, the front of the emission will separate from that of the blast wave induced in the surrounding gas at low pressures. Using Cu and Zn samples, the experimental result showed that the separation of the emission front and blast wave front took place at 4 mm above sample surface for the laser energy of 140 mJ."

"Penggunaan laser untuk berbagai macam aplikasi dewasa ini sudah banyak digunakan oleh masyarakat. Oleh karena itu, untuk mendapatkan hasil lebih baik dalam pengembangan mesin alat pemotong dan sintering pada bahan polymer menggunakan laser diode berdaya rendah, perlu dilakukan analisis system pemotongan dan sinteringnya, baik secara simulasi maupun eksperimen. Bahan polymer yang digunakan adalah acrylic. Untuk simulasi proses pemotongan menggunakan program matlab, sedangkan untuk eksperimen digunakan mesin CNC frais sebagai pergerakan. Dari penelitian ternyata parameter seperti kecepatan, pass, lintasan dan hembusan udara berpengaruh terhadap kedalaman pemotongan pada proses pemotongan, sedangkan ketebalan produk pada hasil proses sintering dipengaruhi parameter seperti kecepatan, tegangan dan arus listrik laser diode dan layer.

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Nowadays the use of laser to various kinds of applications has been applied. Therefore, to obtain better results in the development of a cutting and sintering machine of polymer materials using low power laser, cutting system and sintering should be analyzed, both in simulation and experiment. The polymer materials used in this experiment are acrylic. For the simulation of cutting process, matlab program is used while the experimental process used CNC milling machine as a manipulator.

From the research it is shown that parameters such as speed, pass, path and airflow affect the depth of cutting in the process of cutting, while the thickness of the product on the results of the process of sintering have been influenced by parameters such as speed, voltage and electrical current laser diode and layer."

"ABSTRAKPembuatan mikro kapsul untuk terapi kanker laju dosis rendah memerlukan kualitas yang baik agar tidak berdampak negatif terhadap pemakai. Pengelasan mikro kapsul menggunakan las laser Nd-YAG yang merupakan bagian dari proses pembuatan harus pula dilakukan secara baik. Penelitian ini menganalisis proses pengelasan mikro kapsul dari bahan Ti6Al4V untuk terapi kanker dosis rendah yang dilakukan Pusat Radioisotop dan Radiofarmaka Badan Tenaga Nuklir Nasional (PRR BATAN),untuk mendapatkan pengaturan parameter pengelasan yang optimal. Pengaturan parameter meliputi pengaturan frekuensi, kecepatan las, bentuk pulsa laser, aliran gas selubung dan perhitungan teoritis pelelehan yang terjadi. Berdasarkan analisis hasil penelitian, dengan mengubah bentuk pulsa laser dapat dilakukan pengelasan dengan energi yang lebih rendah 14,54% penurunan daya penuh 40% dan rata-rata daya turun 50,1%, serta penghematan gas argon sebesar 16,67% dan mendapat tembusan pengelasan yang lebih baik.

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AbstractManufacturing process of low dose rate micro-capsules for cancer therapy requires a good quality to avoid the negative impact for the user. Nd-YAG laser welding of the micro capsule, which is part of the manufacturing process, must also be done well. This study analyzes the process of laser welding the micro capsules of Ti6Al4V material for low-dose rate cancer therapy performed radioisotope and radiopharmaceutical Center National Nuclear Energy Agency (PRR BATAN) to obtain the optimal welding parameter settings. Parameter settings include setting the frequency, speed of welding, laser pulse shape, gas flow shield and the theoretical calculations of melting. Based on the analysis of research results, by changing the shape of the laser pulse, welding can be done with a lower energy 14.54% reduction in the full power 40% and an average power decrease 50,1%, and argon gas savings of 16.67% and get better welding penetration."

"Tujuan: Studi ini bertujuan untuk mengetahui efektivitas fotokoagulasi laser 810 nm durasi 20 ms dan 100 ms dalam mencegah progresivitas PDR. Metode: Penelitian ini adalah uji klinis acak tersamar ganda. Sebanyak 28 subyek yang memenuhi kriteria inklusi dibagi menjadi dua kelompok yang terdiri atas 14 subyek untuk menjalani fotokoagulasi laser 810 nm. Pada kelompok pertama mendapatkan laser dengan durasi 20 ms dan kelompok kedua dengan durasi 100 ms. Lesi derajat 3 dengan spot sized 200 μm diaplikasikan pada kedua kelompok. Penilaian progresivitas PDR dilakukan setelah 2 bulan pasca laser dengan menggunakan foto fundus 7 posisi. Fluence, power dan tajam penglihatan dibandingkan di antara kelompok. Hasil: Sebanyak 25 pasien yang mengikuti follow up selama 2 bulan. Proporsi neovaskularisasi yang tidak progresif pada kelompok 20 ms dan 100 ms sebesar 76,9% dan 75,0% (p=1,000). Power yang dibutuhkan dua kali lebih tinggi pada kelompok 20 ms (1000 vs 500 mW; p=0,000). Rerata fluence pada kelompok durasi 20 ms lebih rendah dua kali dibandingkan kelompok durasi 100 ms (15,91 vs 6,36 J/cm2; p=0,000). Perbaikan visus pasca laser pada kelompok 20 ms dan 100 ms sebesar 23,1% dan 33,3 % (p=1,000). Kesimpulan: Durasi 20 ms memiliki kemampuan mencegah progresivitas neovaskularisasi yang sama dibandingkan dengan durasi 100 ms. Fluence yang dibutuhkan lebih rendah pada durasi 20 ms.

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Aim: The aim of this study was to compare the effectiveness of laser photocoagulation 810-nm with 20 ms and 100 ms duration to prevent the progression of proliferative diabetic retinopathy.

Method: This study was prospective double blind randomized clinical trial. Twenty-eight participants who met the inclusion criteria divided into two groups to undergo laser photocoagulation by using 810 nm lasers. One group consisted of fourteen subjects received 100 ms duration and the other received 20 ms duration. Grade 3 burns with a 200 μm spot sized were placed with both modalities. The progression of PDR was evaluated in two months follow up by using seven fields fundus photographs. Fluence, power and visual acuity were compared in this study.

Result: Twenty five subjects completed the two months follow up. Nonprogressive PDR in 100 ms group was 75.0% and in 20 ms was 76.9% (p=1.000). The median power in 20 ms group increased twice than 100 ms group (1000 vs. 500 mW; p=0.000). The median fluence in 20 ms group reduced to one-half of 100 ms group (6.36 vs. 15.91 J/cm2; p=0,000). Improvement of visual acuity in 20 ms and 100 ms was comparable (23,1% vs. 33,3%; p=1,000).

Conclusion: The 20 ms duration showed similar result in preventing the progression of PDR compared to 100 ms duration. The fluence was lower in 20 ms group."