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"ABSTRACTThe carbon dioxide laser is one of the most versatile types on the marked today. It emits infrared radiation between 9 and 11 micrometer (μm) either at a single line selected by the user or on the strongest line in untuned cavities. It can produce continuous output power output powers ranging from well under 1W for scientific applications to many kilowatts for material working. It can generate pulses from the nanosecond to millisecond regimes. Custom made CO2 lasers have produced continues beams of hundreds of kilowatts for military laser weapon research (Hecht 1984) or nanosecond long pulses of 40 kilo joules (kj) for research in laser induced nuclear fusion (Los Alamos National Laboratory 1982). This versatility comes from the fact that there are several distinct types of carbon dioxide lasers. While they share the same active medium, they have important differences in internal structure and more important to the user in lunch oral characteristic. In theory the structural variations could range over a really continuous spectrum, but manufactures have settled on a few standard configurations which meet most user needs. This users see several distinct types, such as waveguide, low power sealed tube, high power following gas, and pulsed transversely excited CO2 lasers. On TEA lasers discharge instabilities make continuous wave operation impractical at gas pressures above about 100 torr (13,3 MPa). How everit is possible to produce pulses lasting tens of nanosecond to microseconds. Such lasers are called transversely excited atmospheric (TEA) lasers because they operate at or near atmospheric pressure, although same times the term is applied to pulsed transversely excited CO2 lasers which operate at higher or lower pressures. The TEA lasers prime attraction of high power per unit volume of laser gas and have fairly complex power requirements because of the nature of their pulsed operation. Typically same energy in the form of electrons or ultraviolet photons is discharged into the laser gas slightly before the main pulse to make it possible to obtain higher output power. In this thesis, basic theory of the Carbon dioxide laser are presented in section II. Section III descibe Optical Transducer. Section IV contains the characterization of carbon dioxide laser with the results and graphs. Finally some conclusion regarding our discussion are summarized in section V."

"Tesis ini menguraikan pengembangan dan pengukuran standar frekuensi pada 88 THz yang didasarkan pada garis E dari transisi P(7) CH4. Untuk maksud tersebut kita menggunakan sebuah laser yang frekuensinya digeser menggunakan efek Zeeman untuk mencapai garis E dari CH4.Laser He-Ne yang digunakan dalam eksperimen ini dibangkitkan menggunakan pelepasan (discharge) RF, yang menghasilkan keluaran laser berderau rendah. Kesesuaian impedansi antara penguatan RF dan laser He-Ne dicapai dengan sangat efektif menggunakan sebuah trafo resonansi.Dari tiga komponen efek Zeeman hanya komponen a digunakan sebagai garis penguat laser dan dua komponen lainnya 6+ dan 7C ditapis oleh uap Methylbromide dan candela Brewster, sehingga laser RF He-Ne berosilasi pada frekuensi tunggal yang dapat diatur dan keluaran laser berderau rendah.Untuk meningkatkan rasio SIN dari pendeteksi spektrum garis absorpsi E, telah dikembangkan sistim dispersi tersaturasi menggunakan laser He-Ne bermode ganda. Sistim ini bekerja sebagai pendeteksi heterodyne internal untuk merekam frekuensi denyut (beat). Sistim ini memperbaiki rasio SIN mencapai faktor 4 sampai 5 kali.Dengan menggunakan sistim tersebut telah dilakukan pengamatan ketergantungan frekuensi pusat garis E terhadap parameter kerja seperti: power laser, lebar modulasi laser dan tekanan methane. Pergeseran frekuensi diukur menggunakan sistim Offset lock dengan komponen pusat dari hyperfineyang terurai sebagai referensi yang stabil. Diperoleh untuk perubahan parameter kerja tertentu pergeseran frekuensi pusat garis E dibatasi antara 100 dan 150 Hz. Juga telah diamati pergeseran frekuensi yang terbesar adalah karena tekanan methane.Untuk pengukuran frekuensi absolut dan garis E, laser Zeeman He-Ne distabilkan menggunakan sebuah sistim deteksi ganda yang unik, yang telah dikembangkan dalam percobaan Penentuan frekuensi absolut garis E dilakukan menggunakan rantai pengukuran frekuensi yang ber-phasa koheren, yang dihubungkan dengan jam Cs dari PTB. Sebagai hasil dari pengukuran ini diperoleh frekuensi pusat garis E :vE = 88 373 149 028 553 ± 230 Hz, ini menunjukkan penambahan ketelitian yang cukup berarti terhadap pengukuran sebelumnya.

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This thesis describes the development and measurement of a frequency standard at 88 THz, based on E-line of P(7) transition of CI-4 For this propose we use a He-Ne laser tuned by Zeeman effect to E-line.

The He-Ne laser used in this experiment is excited by RF-discharge, which gives a low noise laser output. The matching condition of the impedance between RF power amplifier and the He-Ne laser is achieved more effectively by using a resonator transformer.

From three components of the Zeeman effect only 6 component is used as the laser gain line in this experiment and the two a+, n components are suppressed by methylbromide vapour and Brewster window respectively, so that the E-line RF He-Ne laser oscillates at a single adjustable frequency with a low noise laser output.

To enhance the SIN ratio of the detection of the E-line absorption spectrum, a saturated dispersion system using a double mode RF He-Ne laser have been studied and developed. This system works as an ideal internal heterodyne detector for recording the beat frequency. As a result the SIN ratio is improved by a factor of 4 to 5 times.

Employing this detection system has been carried out to study the dependency of the E-line center frequency on the operating parameters such as the laser power, the laser modulation width and the methane pressure. The frequency shift was measured by using an offset lock system with respect to the center component of the hyperfine resolved F2 -line as a stable reference. It was found that within the variation range of the operatings parameters the center frequency shift of the E-line, was limited between 100 and 150 Hz. It was also observed that the largest frequency shift was due to methane gas pressure.

For measurement of the absolute frequency of the E-line, the Zeeman tuned He-Ne laser was stabilized using an unique double detection system, which was developed in this work. The determination of the absolute frequency of the E-line was carried out using a phase coherent frequency measurement chain linked to a Cs clock of PTB. As the result of this measurement the E-line center frequency of CH4 was found to be:

vE = 88 373 149 028 553 ± 230 Hz and this result shows a substantial increasing accuracy over the previous measurements."

"ABSTRAKTelah dibuat suatu sistem Magneto Optical Trap untuk mendinginkan dan memperangkap atom gas yang terdiri dari sepasang kumparan anti Helmholtz dengan 3 pasang cahaya laser pendingin yang dihasilkan dari satu laser dioda, dan satu laser lainnya digunakan sebagai laser pemompa-kembali (repumping laser). Atom Cs diletakkan dalam satu ruang oakum tinggi yang berada di tengah-tengah kumparan anti Helmholtz. Dengan bantuan sistem ini telah dapat diperangkap sekitar 107 atom Cs dan didinginkan sampai temperatur beberapa μK. Gumpalan awan atom ini dapat diamati dan foto luminesensi yang terjadi dalam awan yang didinginkan tersebut.Sifat-sifat dinamika awan atom Cs ini dapat dipelajari dengan mematikan atau mengubah frekuensi laser pendingin dan laser pemompa-kembali secara terprogram dan dengan mengamati luminesensinya. Dengan cara ini dapat dipelajari gejala transien, dan penjarangan populasi yang menyertainya.Selanjutnya telah dilakukan pengukuran temperatur dengan menggunakan metoda balistik yang sudah lazim dilakukan orang. Disamping itu telah dikembangkan cara pengukuran temperatur awan atom yang lebih teliti dengan menggunakan osilasi posisi dari awan atom dengan menggunakan medan magnet dari kumparan Anti Helmhotz yang berosilasi. Temyata metoda ini lebih dapat diandalkan dan hasilnya konsisten dengan metoda yang konvensional.

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ABSTRACT

A Magneto Optical Trap has been built consisting a pair of Anti Helmholtt coils with three pairs of cooling laser beams produced by one laser diode, and the other one for repumping. The Cs atom is placed in a high vacuum chamber located in the center of the anti Helmholtz coils. In this system about 107 Cs atoms have been trap and cooled to a temperature of a few μK. The cloud can be observed from the luminescence of the cooled atoms.

The dynamical properties of the cooled Cs atom has been studied by turning off or changing the frequency of the cooling laser and the repumping laser precisely for a short period and observing the luminescence of the cloud. In this way the characteristics of the transient phenomena of the cloud, such as the build up time, the pumping time and the density of the cooled Cs atoms can be studied.

The temperature of the cooled Cs atom in the cloud has been determined using the well known ballistic method. A new method for the measurement of the temperature of the Cs atoms has been developed. In this new method the position of the cloud is oscillated by a uniform oscillating magnetic field produced from a sinusoidal modulation added to the one of anti Helmholtz coils. The results turns out to be more reliable and the measurement result is consistent with the conventional method."

"ABSTRAKPandu gelombang optik tergandeng telah digunakan secara luas pada sistem komunikasi serat optik sebagai piranti pencabang optik seperti penggandeng arah, demultiplexer, tapis, saklar dan pembagi daya optik. Pandu gelombang tergandeng paralel dengan bentuk yang asimetris dan bentuk tirus/menyempit diketahui mempunyai sifat gandengan yang menarik dan dapat digunakan sebagai piranti pencabang apabila kondisi kerja tertentu dipenuhi. Sifat-sifat gandengan pada pandu gelombang tergandeng dianalisa secara teoritis dengan menggunakan metoda interferensi dua moda dari gelombang yang terpandu. Pemindahan daya secara total pada penggandeng arah tidak dapat terjadi kecuali kecepatan phasa atau tetapan propagasi dari kedua pandu gelombang tersebut sesuai/cocok. Simulasi sifat-sifat gandengan dilakukan dengan Metoda Propagasi Berkas Cahaya. Hasil analisa menyatakan bahwa jamak gandengan dari penggandeng arah simetris akan berkurang dengan bertambahnya panjang gelombang, dan akan berkurang dengan bertambahnya perbedaan indeks bias antara inti dan selubung. Selain itu efisiensi pemindahan days pada pandu gelombang paralel a-simetris akan menurun apabila derajat ketidaksimetrian bertambah. Sifat-sifat ini selanjutnya dapat diterapkan pada sistem pandu gelombang jamak paralel. Selanjutnya berdasarkan teknik interferensi dua moda kita dapat menganalisa karakteristik pemindahan daya dari penggandeng 3-pandu gelombang dan 5-pandu gelombang. Dalam disertasi ini diusulkan struktur baru pembagi daya 1x5 dengan struktur pandu gelombang paralel a-simetris yang mempunyai pembagian daya yang merata dan dapat dioperasikan pada daerah panjang gelombang 1.3 - 1.55 arm.Analisa sifat-sifat gandengan jugs telah dilakukan untuk struktur pandu gelombang tergandeng berbentuk tirus/menyempit. Telah dianalisa sifat gandengan dari pandu gelombang tergandeng berbentuk tirus yang simetris dan a-simetris dengan menggunakan BPM. Telah didapat hasil yang baru, yaitu bahwa penggandeng arah dengan bentuk tirus yang simetris dapat digunakan sebagai penggandeng 3-dB dengan pita panjang gelombang yang luas. Struktur ini sangat efisien sebagai pembagi daya karena ukurannya yang kecil yang disebabkan oleh jarak gandengan yang pendek dan dipertnhankannya pembagian daya yang tetap merata sepanjang arah penjalarannya. Berdasarkan hasil tersebut telah diusulkan bentuk baru pencabang-Y yang mempunyai sifat pembagian daya yang merata yang ditunjukkan oleh basil simulasi BPM. Kedua piranti tersebut telah dibuat dengan teknik Sputtering-RF pada bahan dasar SiO2. Piranti-piranti ini dapat dikembangkaa sebagai pembagi daya IxN, yang dapat digunakan pada sistem komunikasi serat optik WDM dan sistem pemroses sinyal.

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ABSTRACT

Optical coupled waveguide has been widely used in optical communication systems as a branching device such as directional couplers, de-multiplexer, filter, switching device and power divider. Parallel coupled waveguide with asymmetrical structure and tapered form are known to have interesting coupling characteristics and can be utilized as branching devices when certain working requirements are met. The coupling properties in coupled waveguides are analyzed theoretically on the basis of two modes interference effect of the propagating waves. Complete power transfer in directional coupler can not be realized, even if the phase velocity or propagation constant of the two waveguide are matched. Simulation of coupling properties is performed by using Beam Propagation Methods. As a result of the analysis, it is shown that the coupling length of symmetrical directional coupler decreases as the wavelength increases and increases as the index difference between core and cladding decreases. On the other hand, in the parallel asymmetrical structure the power coupling efficiency decreases as the asymmetry of the structure increases. These properties also can be extend applied to multi-parallel wave guide systems. Based on modes interference techniques we can analyze power transfer characteristics of 3-guides and 5-guides couplers. In this dissertation we proposed a novel 1x5 power divider based on asymmetrical parallel coupled waveguides structure which has an evenly power dividing ratio , and can be operated at the wavelength range of 1.3 - 1.55 um.

Analysis of the coupling properties has also been carried out for the tapered-form coupled waveguide structure. We have analyzed coupling characteristics of both asymmetrical and symmetrical tapered-form waveguides by using BPM. We have discovered a new result that the directional coupler with symmetrical tapered-form can be used as a 3-db coupler with a broadband characteristic. This structure is very efficient as a power divider because of its small size due to short coupling length and even power dividing ratio along the propagation direction. Based on this new result obtained from our analysis, we further proposed a novel structure of Y-branch coupler waveguide, which excellent power dividing properties are exhibited by our BPM simulation. Both devices have been fabricated by RF-sputtering technique on SiO2 based material. These devices can be developed as an lxN power splitter, which can be applied in a wide WDM optical communication systems and Signal processing systems."