Al-Khwarizmi Engineering Journal Al-Khwarizmi Engineering Journal, Vol. 6, No. 2, PP 43-50 (2010) 355nm Wavelength Generation of Nd:YAG Laser Using Olive Oil Aqeel S. Fadhil* Anwaar A. Al-Dergazly** Ziad T. Al-Dahan** * Ministry of Oil/ State Company for Oil Projects Email: akeel_man_utd@yahoo.com ** Department of Laser and Electronic Optic/ College of Engineering/ University of Nahrain (Received 27 April 2009; accepted 22 February 2010) Abstract This project introduces a prospective material for photonic laser applications. The material is olive oil which is classified as organic compound, having a good nonlinear optical properties candidate to be used in photonic applications. A high purity sample of olive oil has been used. The theoretical calculation to generate third harmonic wave using olive oil has been determine using MATLAB program. THG (λ=355nm) intensity has been determined at two cases of sample thicknesses 1mm and 10mm. The minimum threshold incident intensity to obtain THG intensity are equal Iω=7530 mW/cm 2 at L=1mm and Iω= 6220 mW/cm 2 at L=10mm. The possibility of generation of third harmonic in olive oil inside the cuvette has been experimented using different powers (90-120) mW of CW Nd:YAG laser. The signal of third harmonic generation has been detected using UV-340 Light Meter. Kewords: Olive oil, Third harmonic generation, THG intensity. 1. Introduction The phenomenon of third harmonic generation (THG) is a well-known manifestation of the cubic optical nonlinearity of materials, χ(3). The efficiency of THG depends on the material nonlinearity, incident light (fundamental) intensity and the length of coherent interaction (sample thickness). High third-order nonlinearities are often reported for various materials, in particular organics [1]. Olive oil an organic material consisted of two main groups of substances: saponifables and unsaponifables. A Saponifables compound contains strong π-electron conjugation. This is a crucial factor in attaining high optical nonlinearities and, indeed olive oil have been considered for applications in which a high value of the nonlinear refractive index, n2 would be of advantage to obtain all-optical switching of optical signals at relatively low light intensities. Also, olive oil can be used in biochemical application because of simplicity and compactness of the system. 2. Theoretical Results and Discussion Firstly, the transmission spectrum of olive oil is determined using UV-VIS spectrophotometer as shown in figure 1. THG intensity can be determined theoretically using the following equation [2].               222)3( 2 2 244 2 3 2/ 2/sin3 IL Lk Lk cn I o    ...(1) This equation shows THG parameters, which are represented by fundamental frequency ω, which are represented by fundamental frequency ω, interaction length or sample thickness L, third order nonlinear susceptibility χ(3) of the material which is determined experimentally using z-scan technique has a value of ≈ 10-12 m2/V2. This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Akeel S. Fadhil Al-Khwarizmi Engineering Journal, Vol. 6, No. 2, PP 43-50 (2010) 44 Fig. 1. Olive oil Transmission Spectrum. Iω represents the excitation intensity of laser beam. c and εo represents, the speed of light and vacuum permittivity. The wave vector at THG signal ∆k is determined from the following equation [2]: )( 6 3 33    nnkkk  ...(2) nω and n3ω respectively, the refractive index at fundamental and THG frequency, which is equal 1.46 and 1.4789 [3]. ω is the fundamental frequency at λ=1064nm, which equals 1.77×1015 Hz. the wave vector ∆k equals 334.8mm-1. THG intensity is determined using the first equation at different input excitation intensity and by using computer program (MATLAB). Two values of interaction length were used in calculations (L=1mm, L=10mm) as shown in figure 2. Fig. 2. THG light Intensity Versus Input Excitation Intensity for Different Interaction Length. 0 0.5 1 1.5 2 2.5 3 3.5 x 10 5 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Excitation intensity(mW/cm 2 ) TH G in te ns ity (m W /c m 2 ) L=1mm L=10mm THG approximatly = 0 This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Akeel S. Fadhil Al-Khwarizmi Engineering Journal, Vol. 6, No. 2, PP 43-50 (2010) ٤٥ From figure 2, the variation in THG intensity is proportional to the square of excitation intensity; the variation is low at (0.0318×105 – 0.122×105 mW/cm2) while after 0.138×105 mW/cm2 for L=1mm and 0.18×105 mW/cm2 for L=10mm the variation increases rapidly until to reach the maximum value at 3.25×105 excitation intensity in this figure. The interaction length L affects the THG intensity. The threshold intensity Ith to obtained THG were found from figure 2 by changing the incident powers in two cases of interaction length, L=1mm and L=10mm as shown in Tables 1 & 2 respectively where the spot area A=πd2/4, d represents the spot diameter was changed between d=0.2mm and 2mm. Then, Ith=4p/πd 2 [2], P is the incident power. Table1, Threshold Values of THG Intensities at L=1mm. Power (mW) Ith (mW/cm2) I3ω (mW/cm) Spot area (mm2) 80 6220 0.01 1.286 100 6310 0.01 1.583 120 13600 0.1 0.882 140 13720 0.1 1.02 Table2, Threshold Values of THG Intensities at L=10mm. Power (mW) Ith (mW/cm2) I3ω (mW/cm2) Spot area (mm2) 80 7570 0.1 1.0568 100 7530 0.1 1.327 120 7170 0.1 1.628 140 15860 1 0.882 The maximum values of THG intensities were observed in the case of phase-matching or non- collinear. Phase-matching can be obtained when the wave vector ΔkL=0 by changing the thickness of sample. Efficient THG is difficult to achieve in the olive oil because the wave vector Δk≠0 and n3ω>nω [2]. In the case of different thickness of sample L, phase-matched THG intensity can be achieved as shown in figures 3. Figures 3 shows the phase-matching and phase mis-matching of THG intensity, which is determined at four values of spot diameter of the fundamental beam d (0.1, 0.12, 0.14, 0.16) mm and for different values of sample thickness L from 10-100 μm in step of 1. Fig.3. Phase-Matched THG Intensity at 80mW Input Power. As a result, phase-matched THG intensity was obtained at the values of sample thickness (10, 28, 46, 66) μm. Phase mis-matched THG intensity was obtained at the values of sample thickness (18, 37, 56, 75, 93) μm. The phase mis- match occurs periodically every 18μm (i.e. the coherent length Lc equal 18μm). Also, the variation of the THG intensity is proportional to the value of spot diameter into phase matching and mis-matching. For the value of spot diameter (d=0.1mm), THG intensity has become at maximum value, while at the value of spot diameter (d=0.16) it has become at minimum value. The reason of this effect is that the incident intensity is increased by reducing the spot diameter. So, for small spot diameter the intensity of incident laser beam becomes very high and THG intensity is increased by increase the intensity of excitation beam. 3. Experimental THG intensity is measured experimentally using a simple set-up in laboratory as shown in figure 5. The set-up was consisted of the following components: 1- Nd:YAG CW infrared laser (λ=1064nm). 2- The sample, which represented the solution of olive oil filled in 1mm quartz cuvette. 3- UV-light meter, which is shown in the figure 5. Figure 4 shows the block-diagram of THG measurements: 10 20 30 40 50 60 70 80 90 100 0 500 1000 1500 Sample thickness(m) T H G i n te n s it y ( m W /c m 2 ) d=0.1mm d=0.12mm d=0.14mm d=0.16mm This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Akeel S. Fadhil Al-Khwarizmi Engineering Journal, Vol. 6, No. 2, PP 43-50 (2010) 46 Fig. 4. Block-Diagram of THG Measurements. Fig. 5. Set-Up of THG Experiment. Assuming a plane wave and non-depleting fundamental power, the THG output power was measured for different incident angles in the range from -30° to 30° increments of 5°step. The measurements of intensity based on two values of sample thickness 1mm and 10mm. The incident angle of fundamental beam θ was changed by tilt the sample forward to the left of the optical axis to make a positive angle and backward to the right of the optical axis to make a negative angle. Bevel- square was used to measure the incident angle. THG output signal intensity was measured with respect to the reference value when the quartz cuvette is blank. At the reference, very low UV radiation was detected, which represented the Rayleigh-scattering or stimulated Raman scattering. This value is regarded in measurements. The efficient values of THG output signal intensity was found as shown in figures 6 to 9: Fig. 6. THG Output Intensity Excited at 90mW Input Power Versus Incident Angle for L=1mm. Fig. 7. THG Output Intensity Excited at 100mW Input Power Versus Incident Angle for L=1mm Fig. 8. THG Output Intensity Excited at 120mW Input Power Versus Incident Angle for L=1mm. Nd:YAG laser SampleDetector -30 -20 -10 0 10 20 30 220 240 260 280 300 320 340 360 380 400 Tilt angle(deg.) T H G i n te n s it y (m w /c m 2 ) data 5th degree -30 -20 -10 0 10 20 30 100 150 200 250 300 350 400 450 Incident angle(deg.) T H G i n te n s it y (m w /c m 2 ) data 7th degree -30 -20 -10 0 10 20 30 20 40 60 80 100 120 140 160 180 Incident angle(deg.) T H G i n te n s it y (m w /c m 2 ) data 7th degree This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Akeel S. Fadhil Al-Khwarizmi Engineering Journal, Vol. 6, No. 2, PP 43-50 (2010) 47 Fig. 9. THG Output Intensity Excited at 110mW Input Power Versus Incident Angle for L=1mm. The result shows different values of THG intensity at each input power due the change in the incident angle of fundamental beam. The reason of change the incident angle of the fundamental beam is to obtain on efficient THG intensity. The change in the incident angle of fundamental beam was induced change in the re- orientation of the olive oil molecules, which induced change in refractive index For L=10mm, THG output signal intensity was measured with respect to the reference value. Very low UV radiation of scattering was detected at the reference (when the cuvette is blank). The efficient THG output signal intensity was found as shown in figures10 to 13: Fig. 10. THG Output Intensity Excited at 90mW Input Power Versus Incident Angle for L=10mm. Fig. 11. THG Output Intensity Excited at 100mW Input Power Versus Incident Angle for L=10mm. Fig. 12. THG Output Intensity Excited at 110mW Input Power Versus Incident Angle for L=10mm. Fig. 13.THG Output Intensity Excited at 120mW Input Power Versus Incident Angle for L=10mm. -30 -20 -10 0 10 20 30 0 50 100 150 200 250 Incident angle(deg.) T H G i n te n s it y (m W /c m 2 ) data shape-preserving -30 -20 -10 0 10 20 30 0 50 100 150 200 250 Incident angle(deg.) T H G i n te n s it y (m W /c m 2 ) data 8th degree -30 -20 -10 0 10 20 30 0 50 100 150 200 250 Incident angle(deg.) T H G i n te n s it y (m w /c m 2 ) data 5th degree -30 -20 -10 0 10 20 30 0 50 100 150 200 250 Incident angle(deg.) T H G i n te n s it y (m W /c m 2 ) data shape-preserving -30 -20 -10 0 10 20 30 120 140 160 180 200 220 240 260 280 Incident angle(deg.) T H G i n te n s it y (m w /c m 2 ) data 7th degree This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Akeel S. Fadhil Al-Khwarizmi Engineering Journal, Vol. 6, No. 2, PP 43-50 (2010) 48 The results show different values of THG intensity for each input power due to the change in the incident angle of fundamental beam. Also, the efficient THG intensity was approximately obtained at incident angle in rang from -15° to 15° because no signal will be detected at the incident angles -20° and 20°. These angles represent the best angles of THG signal because of high re- absorption of THG intensity occurred at these angles. The experimental results were compared with theoretical results as shown in figure 14. Fig. 14. Theoretical and Experimental Values of THG Intensity. From figure 14, the experimental values of THG intensity are in good agreement with theoretical values. This case was obtained when the excitation beam (fundamental beam) was incidence in the medium. Fig. 15. Efficiency of Conversion The Fundamental Beam into THG for L=1mm & L=10mm. The efficiency of the conversion of the fundamental beam into THG beam is determined experimentally using the following formula at L=1mm & L=10 mm for different incident powers as shown in figure 15: ....(3) 4. Conclusions We have reported on efficient third harmonic generation in self-focusing in olive oil solution. We have theoretically determined the threshold intensity to obtained THG intensity in olive oil for two cases of sample thicknesses. For 1mm the threshold intensity to obtained THG equal Iω=7530 mW/cm 2 and for 10mm the threshold intensity to obtained THG equal Iω= 6220 mW/cm2. Also, the coherence length of olive oil is equal to 18μm, which is obtained from the simulation results, when third order nonlinear susceptibility equals ~10-12 m2/V2 for different input powers. THG intensity is changing with the change in the incident angles. The best incident angles are equal -10, 0, +10 degree for L=1mm and +5, 0 degree for L=10mm to obtained the maximum generation. Notation A Spot area of laser beam c Light speed in vacuum d Spot diameter of laser beam Iω, I(0) Incidence intensity I3ω Third harmonic generation intensity Ith Threshold incident intensity to obtain THG kω Wave number of fundamental beam k3ω Wave number of THG beam ∆k Wave vector phase mis-match L Sample length n Total refractive index nω Refractive index at frequency ω n3ω Refractive index at frequency 3ω P Incident power )0( )(3   I LI conversionofEfficiency  7 7.5 8 8.5 9 9.5 10 10.5 11 x 10 4 0 100 200 300 400 500 600 Incident intensity(mW/cm2) T H G i n te n s it y (m W /c m 2 ) theoretical L=1mm theoretical L=10mm experimental L=1mm experimental L=10mm 90 95 100 105 110 115 120 125 130 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 Incident power(mW) E ff ic ie n c y o f T H G % L=10mm L=1mm This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ Akeel S. Fadhil Al-Khwarizmi Engineering Journal, Vol. 6, No. 2, PP 43-50 (2010) 49 Greek letters εo Vacuum permittivity λ Wavelength ω Angular frequency 5. References [1] M. Samoc, A. Samoc, B. Luther-Daives, "Third harmonic autocorrelation and wave mixing in poly(p-phenylenevinylene", Optical Society of America: OPTICS EXPRESS, Vol. 11, No. 15, 1787-1792, (2003). [2] M. G. Pabadopouls, A. J. Sadlej and J. Leszcynski, "Nonlinear optical properties of matter", Springer, Netherlands, (2006). [3]Aqeel Salah Fadhil," Study of Nonlinear Optical Properties of Olive Oil", M.Sc. Thesis, Nahrain university, (2009). This page was created using Nitro PDF trial software. To purchase, go to http://www.nitropdf.com/ http://www.nitropdf.com/ )2010( 50-43 ، صفحة2، العدد 6المجلد مجلة الخوارزمي الھندسیة عقیل صالح فاضل 50 یاك باستخدام زیت الزیتون-نانومتر للیزر الندیمیوم ٣٥٥تولید التوافق الثالث **زیاد طارق الدھان** أنوار عبد الستارالدركزلي* عقیل صالح فاضل ارة النفطوز/ شركة المشاریع النفطیة * Akeel_man_utd@yahoo: البرید االلكتروني جامعة النھرین/ كلیة الھندسة /قسم ھندسة اللیزر وااللكترونیات البصریة ** :الخالصة ة زر الفوتونی ات اللی وي یم . یقدم ھذا المشروع مادة جدیدة مقترحة لتطبیق ب عض نیفھ كمرك ن تص ذي یمك ون ال ت الزیت ي زی ادة ھ ذه الم فات ھ ك مواص تل ون . الخطیة جیدة تمكنھ من استخدامھ في التطبیقات الفوتونیة ث , استخدمت عینة ذو نقاوة عالیة من زیت الزیت ق الثال د التواف ة لتولی ابات النظری اد الحس م ایج ت م و ١نانومتر نظریا على سمكین للعینة ٣٥٥حیث تم ایجاد شدة الطاقة للتولید التوافقي الثالث . باستخدام زیت الزیتون باستخدام برنامج الماتالب م ١٠م ل . م اق .مم١٠لسمك العینة ٢سم/ملي واط ٦٢٢٠مم و تساوي ١لسمك العینة ٢سم/ملي واط ٧٣٥٠قیمة لشدة الطاقة حتى یحصل التوافق الثالث تساوي تخدام تم تو. مم١٠مم و١تم ایجاد شدة الطاقة للتولید التوافقي الثالث على سمكین للمادة , عملیا ة باس لید التوافق الثالث في زیت الزیتون داخل حاویة زجاجی .ملي واط) ١٣٠-٩٠(یاك ذو الموجة المستمرة وبمختلف الطاقات -لیزر الندیمیوم This page was created using Nitro PDF trial software. 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