Nanotechnology and high-precision optical displacement sensor design for optomechatronical systems

Transcription

1 Nanotechnology and high-preciion optical diplaceent enor deign for optoechatronical yte A. Rotai* a, b, c, R. Yadipour a and K. Abbaian a, Z. D. Koozehkanani a, A. Ghanbari b, c, d and F. J. Sharifi e a Photonic and Nanocrytal Reearch Lab., (PNRL), Faculty of lectrical and Coputer ngineering, Univerity of Tabriz, Tabriz 5664, Iran b School of ngineering erging Technologie, Univerity of Tabriz, Tabriz, Iran c Center of xcellence for Mechatronic, Univerity of Tabriz, Tabriz 5664, Iran d Faculty of Mechanical ngineering, Univerity of Tabriz, Tabriz 5664, Iran e Departent of Mechanical ngineering, Ryeron Univerity, Toronto, Canada ABSTRACT In thi paper, nanocrytal are ued to propoe an ultra high-reolution, copact and tunable optical diplaceent enor for optoechatronical yte. In thi propoal nanophotonic principle are ued to develop diplaceent enor which i required trongly in icro and nano achine epecially icro robotic. For thi purpoe, in thi work nanocrytal doped icro ring reonator i ued a baic cell. Then we propoe integrated cae for array application uch a array of icro irror. We how that the propoed enor can eaily detect well below nanoeter to near picoeter range. Alo, it i illutrated that uing lectroagnetically Induced Tranparency () reolution of the propoed enor can be increaed. Finally the propoed tructure i tunable. Keyword- Nanotechnology,, Diplaceent enor, Micro irror. INTRODUCTION Cobination of optical and echanical yte naed optoechatronic or optical icro electroechanical yte (optical-mms) opened new inight to device deign for aking proceing block. Alo, deign trategy baed on optical-mms i uitable approach for enor deign too. For realization of ultra high preciion yte in deep ubicron or nano-cale one of iportant enor i diplaceent enor. So, for realization of thi enor different ethod have been ued. Here, we are going to review oe of the and invetigate advantage and diadvantage of the reported work. Soe of tandard diplaceent ening ethod in technology counity i ued uch a uing variable reitance a phyical phenoenon for detection of the object diplaceent, uing capacitance eauring, uing piezoelectric aterial, change of air gap in tranforer which introduce variable induced voltage and advanced verion of thi ethod for diplaceent eaureent i linear variable differential tranforer (LVDT) []. Thi type of diplaceent enor cover ub-icron to range of operation. Ultraound ethod i another intereting approach for diplaceent onitoring. In thi ethod ultraound pule applied to the object and backward wave i detected. Baed on forward tranitting and backward receiving wave the object diplaceent i calculated []. Since wavelength of the ultraound wave i high enough, o preciion of the diplaceent eaureent i low. Optical ethod i another iportant technique for diplaceent eaureent. Thi approach wa dicued in [-4]. In thi ethod two baic technique are ued. One of thee ethod baed on the reflected back intenity. In thi technique variation of diplaceent converted to the level of intenity eaured with high reolution photodetector. Interference of the forward and backward traveling wave and phae difference i another criterion of the diplaceent eaureent. In thee ethod diplaceent reolution can be * rotai@tabrizu.ac.ir; phone ; fax

2 increaed to near Pico eter range. In thee enor range of operation uually liited to icro eter range. Another intereting ethod developed recently i baed on ring reonator and ued for high reolution diplaceent eaureent [5]. In thi ethod uually a narrow gap i ade on top part of the ring and outgoing wave fro thi gap ipact on object and reflected back to the ring. On the other hand object and ring iultaneouly introduce a reonant cavity. Diplaceent of object change the ocillation and reonance frequency of the coplex yte. So, eauring of output intenity for input light at given wavelength i ued for eaureent of the diplaceent. Micro-ring reonator i a baic and iportant device which i ued recently ore [6-4] a the building block for optical yte uch a filter. So, in thi paper we have propoed array of nanocrytal doped icro reonator a an ultra-high preciion diplaceent enor with equal pacing between adjacent reonator without coupling where each of the are coupled to a waveguide. Thu the array i coupled to an input and output bu waveguide. There i a baic proble with ring reonator. It i wide pectral hape which caue low preciion in diplaceent eaureent. For thi purpoe in thi paper we preent a new idea for iproving thi proble. Our ethod i baed on doping of ring reonator with -level ato or nanocrytal. In thi ituation the pectral profile of the ring reonator i decreaed trongly and thu the preciion of the enor i increaed. For thi propoal, we ue quantu optical tool for decription of optical propertie of the nanocrytal doped ring reonator [5]. In thi propoal, we ued -level ato with given denity. Firt, we calculate the optical uceptibility and then uing control field changing of the obtained uceptibility i controlled. Obtained optical uceptibility i ued for anageent of the guided wave and finally optical output intenity i extracted. Since obtained optical uceptibility deterine the reonance frequency, o applied light in a given wavelength ay have different output intenity in the output port. So, ultra all narrowband pectral profile can be ued for obtaining on-off behavior in the output for all diplaceent. We how that our propoed ethod can eaure well below nanoeter range. Organization of thi paper i a follow: In ection theoretical background for decription of the tructure i preented. Nuerical iulation reult are preented and dicued in ection. Finally the paper end with a hort concluion.. THORTICAL BACKGROUND Propoed diplaceent enor tructure with a icro-ring reonator i hown in Fig.. Thi cheatic include a waveguide coupled to a ring reonator which i copleted by light propagation and reflection through clean urface of the oving object. By variation of the ditance of the object fro ring the reonance frequency of the ring reonator i changed which i ued to eaure unknown diplaceent ditance. Firt, we calculate the tranfer function of noral (without nanocrytal) ring reonator a follow. Fig.. A ingle ring a baic cell of array

3 According to light propagation in linear and iotropic edia the following relation are preented to decribe the illutrated coupler input-output function. 6 5 = γ.[ K. j K. ], () 5 = γ.[ K. j K. ], () where γ and K are coupler lo and the coupling coefficient repectively. Uing the wave propagation inide ring reonator, two aligned waveguide end, free pace part and reflection fro aple urface, we have α. L ( jβ. L = e e ), () ' 4 ' α. h ( jβ. h = e e ), (4) ' = r. e 5 4 α. α. h ( jβ. e ), (5) ' ( jβ. h = e e ), (6) 4 ( jβ. L45 = e e ), (7) 4 α. L45 whereα and β are the ring (and fiber) lo coefficient and wave propagation vector repectively. Alo, α and β are lo and wave vector of free pace repectively too. The appeared L and L 45 paraeter are length of two part of the ring reonator. Alo, h and are fiber and free pace length a illutrated in Fig. repectively. Finally r i the reflection coefficient of the reflecting urface of the object. After oe atheatical anipulation the following tranfer function i obtained a follow. Thi equation can be ued for evaluation of the noral ring reonator baed optical diplaceent enor. α. L jβ. L α. L ( )( ) α h j β h α j β ( )..e.e.e.e.e.e.e jβ L γ K γ r.e 6 = α. L jβ. L α. L ( )( )..e.e α h j β h α j β.e.e.e.e.e jβ L γ K r.e, () Now, we are going to develop atheatical ethod to decribe effect of -level dopant, on characteritic of deigned diplaceent enor. Uing Λ type -level nanocrytal in ring reonator, we how that the reolution of the propoed enor can be increaed and tuned optically. Fig. how Λ type -level particle cheatic including probe and control field and decay rate. In the odel the control and probe field applied between level - and level - repectively. Due to applied electric field the optical characteritic i changed and in the following brief theoretical calculation for decription of the yte perforance i preented. With trong

4 control and weak probe laer pule, the tie evolution of coherence between atoic level are decribed by following equation []: d i [ H, ] dt ρ = ħ ρ Γρ, (9) where H, ρ and Γ are the yte Hailtonian, denity and decay rate atrixe repectively. Fig.. Scheatic of -level particle After oe atheatical anipulation [], the real and iaginary part of optical uceptibility are given a ' N γ = µ χ a ab γ ε 4 ħz Ω ( + ) + γ γ γ γ, () N γ Ω ( + ) µ χ"= a ab γ γ γ γ γ, () ε 4 ħz where Ω Z = µ γ ( ) γ + γ 4 + γ and = ω υ, γ ab, γ, γ, Ωµ and N a are detuning of probe frequency fro reonance, decay rate of atoic level population, Rabi frequency of control field and denity of doped nanocrytal. Baed on baic and fundaental relation between optical uceptibility and aborption coefficient and refractive index, we have the following relation. κ χ " α =, χ' δn = n, () Finally the propagating wave vector in ring reonator doped with -level particle i given in the following. υn β =, () c Fig. how the diplaceent enor icro-ring array that it output relation are given by equation () or with following equation, which i invetigated nuerically.

5 α. L jβ. L α. L jβ. L 4 α. h j β. h α. j β. 4 ( γ)( K ) ( γ). r.e.e.e.e.e.e.e.e oi = α. L jβ. L α. L jβ. L45 i 4 α. h j β. h α. j β. 4 ( γ)( K ). r.e.e.e.e.e.e.e.e (4) Fig.. Micro-ring array of Senor In the following ection nuerical iulation reult of the propoed tructure are given and dicued in detail.. NUMRICAL SIMULATION RSULTS In thi ection, to evaluate effect of on the traniion coefficient of the propoed tructure, real and iaginary part of the optical uceptibility are illutrated with different control field in Fig.4. It i oberved that with increaing of the control field lope of the linear part of optical uceptibility in central part i decreaed and iniu region of the iaginary part correponding to central part i broadened.

6 x -.5 Two Part of Suceptibility Iaginary Real x -9 a x -.5 Two Part of Suceptibility Iaginary Real x -9 b 7 Fig.4. Two part of optical uceptibility a) C = 4 V, b) C = V λ =.55µ lo =, γ =, γ = γ =, = e c N = c ab a, Then for entioned above cae the traniion coefficient i illutrated and effect of the control field on thi coefficient i hown in Fig.5 and 6. Thee figure illutrate effect of length of ring reonator on enitivity of the deigned enor. It i oberved that with increaing the ring length the traniion coefficient i changed harply and period of ocillation in wavelength doain i decreaed.

7 Noral x -9 a Noral x -9 b

8 Noral x -9 c Fig.5. of optical Diplaceent Senor baed on Ring Reonator a) with µ Ring Length, b) with µ ring Length and c) with 5 µ ring Length for µ diplaceent. h = 5µ = µ K γ = γ = =.4, r =.9, λ =.55µ lo =, α =, ab = e c N a = c, control = 4 7 V /, α =., γ =, Noral x -9 a

9 Noral x -9 b Noral x -9 c Fig.6. of optical Diplaceent Senor baed on Ring Reonator a) with µ peripheral, b) with µ peripheral and c) with 5 µ peripheral for µ diplaceent. h = 5µ = µ K γ = γ = =.4, r =.9, λ =.55µ lo =, ab = e c N a = c, control =, α = V /, α =., γ = In Fig. 5 and 6, it i oberved that with increaing of the control field, not only the ocillatory part of the traniion coefficient i extended to large wavelength duration but alo reolution of the preented enor i increaed.,

10 Fig. 7 and how effect of the control field on traniion coefficient with increaed diplaceent (=5 µ). It i een that with increaing diplaceent the period of ocillation in wavelength doain i decreaed, alo Noral x -9 a Noral x -9 b

11 Noral x -9 c Fig.7. of optical Diplaceent Senor baed on Ring Reonator a) with µ, b) with µ and c) with 5 µ Ring Length for 5 µ diplaceent. h = 5µ = µ K γ = γ =, =.4, r =.9, λ =.55µ lo = ab = e c N a = c, control = 4, α = 7 V /, α =., γ =, Noral x -9 a

12 Noral x -9 b Noral x -9 c Fig.. of optical Diplaceent Senor baed on Ring Reonator a) with µ b) with µ and c) with 5 µ Ring Length for 5 µ diplaceent. h = 5µ = µ K γ = γ = =.4, r =.9, λ =.55µ lo =, ab = e c N a = c, control =, α = V /, α =., γ =, ffect of diplaceent on the traniion coefficient for different diplaceent value are illutrated in Fig. 9. It i hown that thi enor i o enitive that ub nanoeter diplaceent can be ened eaily.

13 .7.6 L 45 = L α = x -9 Fig.9. of optical Diplaceent Senor for different value of diplaceent = 4µ h = 5µ = Legend Value, K, α =., γ =, γ =.4, r =.9, λ =.55µ lo = = γ =, ab = e c N a = c, control =, V / Finally, effect of control field aplitude on the diplaceent enor i invetigated. In Fig., it i oberved that with increaing control field the ocillation period in wavelength doain change which can be ued in detection of agnetic field L 45 γ = = L. e7 9 e7 e.e x -9 Fig.. of optical Diplaceent Senor for different value of applied control field. = 4µ h = 5µ = 5µ K, γ = γ = =.4, r =.9, λ =.55µ lo =, ab = e c N a = c, control =, α = LegendValue V /, α =.,

14 In thi ection different apect of the propoed tructure or high preciion diplaceent enor were evaluated preciely. We have hown that the propoed tructure have potential for high preciion diplaceent ening epecially for optical MMS yte. CONCLUSION In thi paper an ultra-high preciion optical diplaceent enor uing electroagnetically induced tranparency () in icro-ring reonator array ha been preented. It wa hown that the propoed ethod introduce well over oe hundred tie better reolution than noral cae. ffect of different yte paraeter on operation and enor enitivity have been conidered and evaluated.. RFRNCS [] Dandridge A., [Fiber Optic Senor Baed on the Mach-Zehnder and Michelon Interferoeter, in Fiber Optic Senor: An Introduction for ngineer and Scientit], Wiley, New York, (99). [] Kerey A. D., [Ditributed and Multiplexed Fiber Optic Senor: An Introduction for ngineer and Scientit], Wiley, New York, (99). [] Voller F., Ficher P., "Frequency-doain diplaceent ening with a fiber ring-reonator," Senor and Actuator A 4, 4 4, (7). [4] Rotai A., Rotai G., "Full optical analog to digital (A/D) converter baed on Kerr-like nonlinear ring reonator," Optic Counication, pp. 9 4, (). [5] Rotai A. and Abbaian K., "All-optical Filter Deign: lectroagnetically Induced Tranparency and Ring Reonator," Proceeding of ICT-MICC 7, Malayia, Penang, (7). [6] Kiyat I., Kocaba C., Aydinli A., "Integrated Microring Reonator Diplaceent Senor for Scanning Probe Microcope," J. Microechanical Microng., 4, pp. 74-7, (4). [7] White I. M., Zhu H., Suter J. D., Ovey H., Fan X., "Liquid Core Optical Ring Reonator Senor," Optic Letter, pp. 9-, (6). [] Lee H., Fleichhauer M., Scully M. O., "Senitive Detection of Magnetic Field including their orientation with a Magnetoeter baed on atoic phae coherence," Phy. Rev. A, Vol. 5, No., (99). [9] Hot C. M. K., "Deign and Modeling of Waveguide Coupled Single Mode Microring Reonator," J. Lightwave Technology 6, pp , (99). [] Okaura H., Iwatuki K., "A Finee-nhanced r Doped Fiber Ring Reonator," J. Lightwave Technology 9, pp , (99). [] Lopez J. M., [Handbook of Optical Fiber Sening Technology], d. Wiley, Chicheter, (). [] Niu J. X., Zhou X. L., and Wu L. S., "Analyi and Application of Novel Structure Baed on Split Ring Reonator and Coupled Line," Progre In lectroagnetic Reearch, PIR 75, 5-6, (7). [] Scully M. O. and Zubairy M. S., [Quantu Optic], Cabridge Univerity Pre, (997). [4] Rotai A. and Rotai G., [Linear and nonlinear Application of Ring Reonator], Book Chapter, Nova Publiher, USA (7).