FI-196 Eletr nica Qu ntica: LASERS ifi.unicamp.br

1. 25/8/2012 Fl�vio Cruz / FI-196 1 FI-196 Eletr�nica Qu�ntica: LASERShttp://www.ifi.unicamp.br/lasers/FI196 Prof. Fl�vio C. Cruz flavio@ifi.unicamp.br Tel 3521-5406 Depto de Eletr�nica Qu�ntica IFGW/UNICAMP

2. 25/8/2012 Fl�vio Cruz / FI-196 2

3. 25/8/2012 Fl�vio Cruz / FI-196 3 Aula 1 Introdu��o Hist�ria e Aplica��es O maser de am�nia (NH3) Partes de um laser Tipos de lasers

4. 25/8/2012 Fl�vio Cruz / FI-196 4 Bibliografia VERDEYEN, J.T., Laser Electronics, Prentice Hall, 3rd edition, 1995. SIEGMAN, A.E., Lasers, University Science Books, 1986. YARIV, A., Optical Electronics, 1991. YARIV, A., Quantum Electronics, John Wiley & Sons, NY, 3rd edition, 1989. SVELTO, O., Principles of Lasers, Plenum Press, NY, 1976. SARGENT III, M., SCULLY,M.O. & LAMB, W.E., Laser Physics, Addison-Wesley, 6th printing, 1993; etc..

5. 25/8/2012 Fl�vio Cruz / FI-196 5 Bibliografia Auxiliar MOORE, J.H., DAVIS, CAPLAN, M.A., Building Scientific Apparatus, 2nd edition, 1989. DEMTR�DER, W., Laser Spectroscopy, Springer, 1996. FOWLES, G.R., Introduction to Modern Optics, 2nd edition, 1989. FEYNMAN, R., The Feynman Lectures of Physics. Peri�dicos diversos : OSA: Optics Letters; Optics Express; Applied Optics; Journal of Opticsl Society of America A, B; Optics Communications; Applied Physics; IEEE Journal of Quantum Electronics.

6. 25/8/2012 Fl�vio Cruz / FI-196 6 Handbooks, Revistas e Web Sites The Laser Handbook, Vol 1 to 5; (aquisi��es recentes da biblioteca) Handbook of Lasers; Photonics Spectra, www.photonics.com (revista gr�tis) Laser Focus World, www.optoelectronics-world.com (revista gr�tis), optoeletr�nica, tecnol. fot�nica, aplica��es e mercado Lightwave www.lw.pennnet.com , tecnologia de fibras �pticas Physics 2000, http://www.colorado.edu/physics/2000/index.pl , site educacional Fiber Optics Online, www.fiberopticsonline.com Communications Industry Researchers, www.cir-inc.com Optical Society of America, www.osa.org Am. Inst. Physics, www.aip.org , Am. Phys. Society (APS), www.aps.org Sociedade Brasileira de F�sica, www.sbf.org.br , CBO (comiss�o brasileira de �ptica) IEEE Laser & electro-optics society (LEOS), http://www.ieee.org/portal/site/leos/ Georgia Tech http://www.physics.gatech.edu/people/faculty/rtrebino.html ; usaremos material do Prof. Rick Trebino nas aulas Oregon Center of Optics www.uregon.edu CREOL, http://www.creol.ucf.edu/ Wikipedia, http://www.wikipedia.org/

7. 25/8/2012 Fl�vio Cruz / FI-196 7 Confer�ncias SPIE conference: Photonics West (http://spie.org/photonics-west.xml )

8. 25/8/2012 Fl�vio Cruz / FI-196 8 Confer�ncias

9. 25/8/2012 Fl�vio Cruz / FI-196 9 Avalia��o Lista de exerc�cios (L); Semin�rios + paper (S); Prova (P) M�dia Final : MF = 0.4L + 0.3P +0.3 S Conceitos: A: 9-10; B: 7.5-9; C: 6-7.5

10. 25/8/2012 Fl�vio Cruz / FI-196 10 Aplica��es em Pesquisa Espectroscopia (n�o-linear, alta resolu��o, coerente, resolvida no tempo, etc); confinamento e resfriamento de �tomos (cria��o de condensados de Bose-Einstein); microscopia, imagens (OCT) Interferometria: girosc�pios (�pticos e at�micos), detec��o de ondas gravitacionais; Metrologia de comprimento, tempo e frequ�ncia; Controle coerente: controle de rea��es qu�micas; Separa��o de is�topos, purifica��o; etc..

11. 25/8/2012 Fl�vio Cruz / FI-196 11 Aplica��es Tecnol�gicas e Industriais Processamento de materiais, micromec�nica; Medidas e inspe��o; Leitura, escrita e grava��o de informa��es; Proje��o e displays; Comunica��es �pticas; Holografia; Espectroscopia e Qu�mica Anal�tica; Sensoreamento Remoto; Constru��o Civil; etc..

12. 25/8/2012 Fl�vio Cruz / FI-196 12 Faixa Espectral de Lasers

13. 25/8/2012 Fl�vio Cruz / FI-196 13 Faixa Espectral de Lasers

14. 25/8/2012 Fl�vio Cruz / FI-196 14 Breve Hist�rico 1930: Toda a teoria necess�ria j� estava pronta. (Maxwell, Planck, Einstein). � preciso a Mec�nica Qu�ntica para entender o funcionamento do laser ?

15. 25/8/2012 Fl�vio Cruz / FI-196 15 Breve Hist�rico - continua��o 1954: O maser baseado em feixe de NH3 (am�nia), desenvolvido na Universidade de Columbia por Charles Townes, James Gordon, Herbert Zeiger, seguidos por Nikolai Basov e Alexander Prokhorov da USSR; f = 24 GHz. MASER : Microwave Amplification by Stimulated Emission by Radiation. (este acr�nimo surgiu em 1955). 1954-58: Grande progresso te�rico e experimental; Nicolaas Bloembergen em 1956 prop�e o maser de 3 n�veis para obter a invers�o de popula��o.

16. 25/8/2012 Fl�vio Cruz / FI-196 16 Hist�rico 1958 � A.L. Schawlow e C.Townes � importante artigo sobre possibilidade de �maser �ptico�. Disputa sobre patente devida a Gordon Gould (estudante de p�s na univ. Columbia);

17. 25/8/2012 Fl�vio Cruz / FI-196 17 Inventores do laser

18. 25/8/2012 Fl�vio Cruz / FI-196 18 1� Confer. Internac. de Eletr�nica Qu�ntica - 1959

19. 25/8/2012 Fl�vio Cruz / FI-196 19 P�gina do Caderno de Laborat�rio de Townes

20. 25/8/2012 Fl�vio Cruz / FI-196 20 Hist�rico 1960 : Primeiro maser ��ptico�, ou laser, demonstrado por Theodore (Ted) H.Maiman, do Hughes Research Center, feito com rubi (Cr3+ : Al2O3) bombeado por l�mpada (f= 432 THz; ?= 694 nm);

21. 25/8/2012 Fl�vio Cruz / FI-196 21 Breve Hist�rico - continua��o Uma vez que a teoria estava pronta desde 1930, por que o laser demorou tanto tempo para ser inventado ? D�cadas de 60 e 70 em diante - �explos�o� da �rea, com uma infinidade de tipos de lasers demonstrados em laborat�rio e in�meros deles produzidos comercialmente; Est�gio atual - Ainda caracterizado pelo desenvolvimento tecnol�gico; melhoramentos em lasers �mais antigos�; cobertura de novas regi�es espectrais; novas aplica��es.

22. 25/8/2012 Fl�vio Cruz / FI-196 22 O Maser de Hidrog�nio

23. 25/8/2012 Fl�vio Cruz / FI-196 23 O Maser de Hidrog�nio

24. 25/8/2012 Fl�vio Cruz / FI-196 24 O maser de NH3 (am�nia)

25. 25/8/2012 Fl�vio Cruz / FI-196 25 NH3 - barreira de potencial

26. 25/8/2012 Fl�vio Cruz / FI-196 26 Tunelamento do �tomo de N

27. 25/8/2012 Fl�vio Cruz / FI-196 27 Caso An�logo - Dois p�ndulos acoplados

28. 25/8/2012 Fl�vio Cruz / FI-196 28 Sistema de 2 n�veis

29. 25/8/2012 Fl�vio Cruz / FI-196 29 Distribui��o T�rmica

30. 25/8/2012 Fl�vio Cruz / FI-196 30 Diagrama Experimental do Maser de NH3

31. 25/8/2012 Fl�vio Cruz / FI-196 31 Cavidade de Microondas

32. 25/8/2012 Fl�vio Cruz / FI-196 32 Superposi��o de Estados

33. 25/8/2012 Fl�vio Cruz / FI-196 33 Momento de Dipolo El�trico Oscilante

34. 25/8/2012 Fl�vio Cruz / FI-196 34 Condi��es �timas no Maser

35. 25/8/2012 Fl�vio Cruz / FI-196 35 Partes de um Laser Meio ativo + mecanismo de bombeamento + cavidade �ptica

36. 25/8/2012 Fl�vio Cruz / FI-196 36 Perguntas ... Como excitar o sistema para obter o ganho G ? Os espelhos s�o �especiais� ? Por que os espelhos s�o curvos ? Por que as janelas tem esta orienta��o ? Qual a pot�ncia que pode ser obtida ? A luz � polarizada? Qual seu espectro? etc...

37. 25/8/2012 Fl�vio Cruz / FI-196 37 Alguns Artigos Hist�ricos Gordon, J.P., Zeiger, H.J. and Townes, C.H., Phys.Rev., 99, 1264 (1955). Schawlow, A.L. & Townes, C.H., Infrared and Optical Masers, Phys.Rev. 112:1940, 1958. Maiman, T.H., Stimulated Optical Radiation in Ruby Masers, Nature, 187:493, 1960. Maiman, T.H., Optical and Microwave-Optical Experiments in Ruby, Phys. Rev. Lett., 4:564, 1960. Lamb, W.E. Jr., Theory of an Optical Maser, Phys.Rev., 134:A1429, 1964. De Maria, A.J., Mode Locking, Electronics, Sept.16, p.112, 1968. De Maria, A.J., Picosecond Laser Pulses, Proc.IEEE, 57:3, 1969.

38. 8/25/2012 Fl�vio Cruz / FI-196 38 Types of Lasers Solid-state lasers have lasing material distributed in a solid matrix (such as ruby or neodymium:yttrium-aluminum garnet "YAG"). Flash lamps are the most common power source. The Nd:YAG laser emits infrared light at 1.064 nm. Semiconductor lasers, sometimes called diode lasers, are pn junctions. Current is the pump source. Applications: laser printers or CD players. Dye lasers use complex organic dyes, such as rhodamine 6G, in liquid solution or suspension as lasing media. They are tunable over a broad range of wavelengths. Gas lasers are pumped by current. Helium-Neon lases in the visible and IR. Argon lases in the visible and UV. CO2 lasers emit light in the far-infrared (10.6 mm), and are used for cutting hard materials. Excimer lasers (from the terms excited and dimers) use reactive gases, such as chlorine and fluorine, mixed with inert gases such as argon, krypton, or xenon. When electrically stimulated, a pseudo molecule (dimer) is produced. Excimers lase in the UV. Slide provided by Optics I student Kham Ho, 2004Slide provided by Optics I student Kham Ho, 2004

39. 8/25/2012 Fl�vio Cruz / FI-196 39 The Ruby Laser

40. 8/25/2012 Fl�vio Cruz / FI-196 40 The Helium-Neon Laser

41. 8/25/2012 Fl�vio Cruz / FI-196 41 Carbon Dioxide Laser Vibrational energy level diagram depicting the 10.6 micron infrared transition in the carbon dioxide molecule. (The nitrogen vibrational levels shown on the right are used to enhance lasing in laboratory lasers) Image from http://home.achilles.net/~ypvsj/history/mars.htmlVibrational energy level diagram depicting the 10.6 micron infrared transition in the carbon dioxide molecule. (The nitrogen vibrational levels shown on the right are used to enhance lasing in laboratory lasers) Image from http://home.achilles.net/~ypvsj/history/mars.html

42. 8/25/2012 Fl�vio Cruz / FI-196 42 CO2 laser in the Martian atmosphere The small red circle centered on Chryse Planitia represents the region over which the laser emissions were detected. Solar radiation is responsible for pumping a population inversion in the carbon dioxide of the tenuous upper levels of the atmosphere of Mars (Mumma et al., 1981) and Venus (Deming et al., 1983). Population inversions have also been found in comets (Mumma, 1993). On mars, the solar pump intensity is strongest near the solar point, and falls off gradually towards the terminator. There is some locus where the inversion vanishes, but it is difficult to say exactly where that is. The R(8) transition at 10.33 microns in the infrared is produced from one vibrational quanta of asymmetric stretching to one quantum of symmetric stretching with a change of one quantum of rotational energy from J=8 to J=7. (mars image courtesy : Philip James, University of Toledo; Steven Lee, University of Colorado; and NASA Hubble Space Telescope) Due to the low densities of the lasing species in the mesosphere and thermosphere of Mars the gain is very low, about 10 percent, comparable to single-pass gains in some earth based CO2 lasers. The low gain is partly compensated by the extremely large volumes of active lasing medium. Over the very long distances scales, the exponential properties of amplified spontaneous emission produce a significant spectral signature at the lasing frequency. The laser amplification has been confirmed by several groups (Gordiets et al., Stepanova et al. and Dickinson et al.) Spectra of martian CO2 emission line as a function of frequency difference from line center (in MHz). Blue profile is the total emergent intensity in the absence of laser emission. Red profile is gaussian fit to laser emission line. Radiation is from a 1.7 arc second beam (half-power width) centered on Chryse Planitia (long +41 lat +23).(Mumma et al., 1981) Image from http://home.achilles.net/~ypvsj/history/mars.html The small red circle centered on Chryse Planitia represents the region over which the laser emissions were detected. Solar radiation is responsible for pumping a population inversion in the carbon dioxide of the tenuous upper levels of the atmosphere of Mars (Mumma et al., 1981) and Venus (Deming et al., 1983). Population inversions have also been found in comets (Mumma, 1993). On mars, the solar pump intensity is strongest near the solar point, and falls off gradually towards the terminator. There is some locus where the inversion vanishes, but it is difficult to say exactly where that is. The R(8) transition at 10.33 microns in the infrared is produced from one vibrational quanta of asymmetric stretching to one quantum of symmetric stretching with a change of one quantum of rotational energy from J=8 to J=7. (mars image courtesy : Philip James, University of Toledo; Steven Lee, University of Colorado; and NASA Hubble Space Telescope) Due to the low densities of the lasing species in the mesosphere and thermosphere of Mars the gain is very low, about 10 percent, comparable to single-pass gains in some earth based CO2 lasers. The low gain is partly compensated by the extremely large volumes of active lasing medium. Over the very long distances scales, the exponential properties of amplified spontaneous emission produce a significant spectral signature at the lasing frequency. The laser amplification has been confirmed by several groups (Gordiets et al., Stepanova et al. and Dickinson et al.) Spectra of martian CO2 emission line as a function of frequency difference from line center (in MHz). Blue profile is the total emergent intensity in the absence of laser emission. Red profile is gaussian fit to laser emission line. Radiation is from a 1.7 arc second beam (half-power width) centered on Chryse Planitia (long +41 lat +23).(Mumma et al., 1981) Image from http://home.achilles.net/~ypvsj/history/mars.html

43. 8/25/2012 Fl�vio Cruz / FI-196 43 The Helium Cadmium Laser Text from http://www.shef.ac.uk/physics/teaching/phy332/laser_notes.pdfText from http://www.shef.ac.uk/physics/teaching/phy332/laser_notes.pdf

44. 8/25/2012 Fl�vio Cruz / FI-196 44 The Argon Ion Laser Population inversion is achieved in a two step process. First of all, the electrons in the tube collide with argon atoms and ionize them according to the scheme: Ar (ground state) + lots of energetic electrons � Ar+ (ground state) + (lots + 1) less energetic electrons . The Ar+ ground state has a long lifetime and some of the Ar+ ions are able to collide with more electrons before recombining with slow electrons. This puts them into the excited states according to: Ar+ (ground state) + high energy electrons � Ar+ (excited state) + lower energy electrons . Since there are six 4p levels as compared to only two 4s levels, the statistics of the collisional process leaves three times as many electrons in the 4p level than in the 4s level. Hence we have population inversion. Moreover, cascade transitions from higher excited states also facilitates the population inversion mechanism. The lifetime of the 4p level is 10 ns, which compares to the 1 ns lifetime of the 4s level. Hence we satisfy tupper > tlower and lasing is possible. Table from http://www.eio.com/repairfaq/sam/laserarg.htm#argbcs Energy level diagram from http://www.shef.ac.uk/physics/teaching/phy332/laser_notes.pdf Population inversion is achieved in a two step process. First of all, the electrons in the tube collide with argon atoms and ionize them according to the scheme: Ar (ground state) + lots of energetic electrons � Ar+ (ground state) + (lots + 1) less energetic electrons . The Ar+ ground state has a long lifetime and some of the Ar+ ions are able to collide with more electrons before recombining with slow electrons. This puts them into the excited states according to: Ar+ (ground state) + high energy electrons � Ar+ (excited state) + lower energy electrons . Since there are six 4p levels as compared to only two 4s levels, the statistics of the collisional process leaves three times as many electrons in the 4p level than in the 4s level. Hence we have population inversion. Moreover, cascade transitions from higher excited states also facilitates the population inversion mechanism. The lifetime of the 4p level is 10 ns, which compares to the 1 ns lifetime of the 4s level. Hence we satisfy tupper > tlower and lasing is possible. Table from http://www.eio.com/repairfaq/sam/laserarg.htm#argbcs Energy level diagram from http://www.shef.ac.uk/physics/teaching/phy332/laser_notes.pdf

45. 8/25/2012 Fl�vio Cruz / FI-196 45 The Krypton Ion Laser http://www.eio.com/repairfaq/sam/laserarg.htm#argbcs http://www.lasingonline.com/images/productos/laseres/Gas/297%20mini.jpghttp://www.eio.com/repairfaq/sam/laserarg.htm#argbcs http://www.lasingonline.com/images/productos/laseres/Gas/297%20mini.jpg

46. 8/25/2012 Fl�vio Cruz / FI-196 46 Dye lasers Duarte and Piper, Appl. Opt. 23, 1391 1984Duarte and Piper, Appl. Opt. 23, 1391 1984

47. 8/25/2012 Fl�vio Cruz / FI-196 47 A dye�s energy levels The lower laser level can be almost any level in the S0 manifold.

48. 8/25/2012 Fl�vio Cruz / FI-196 48 Dyes cover the visible, near-IR, and near-UV ranges.

49. 8/25/2012 Fl�vio Cruz / FI-196 49 Titanium: Sapphire (Ti:Sapphire) Slide used with permission from Dan MittlemanSlide used with permission from Dan Mittleman

50. 8/25/2012 Fl�vio Cruz / FI-196 50 Diode Lasers

51. 8/25/2012 Fl�vio Cruz / FI-196 51 Some everyday applications of diode lasers Slide provided by Optics I student Kham Ho, 2004Slide provided by Optics I student Kham Ho, 2004

52. 8/25/2012 Fl�vio Cruz / FI-196 52 A laser in space http://home.achilles.net/~ypvsj/news/EtaCarinae.html P Cygni emission line profile of triply ionized carbon at 1548.2 � in the central star of the cat's eye planetary nebula, NGC 6543. Courtesy of the International Ultraviolet Explorer (IUE). Huggins and Miller were the first to observe the spectra of nova T Coronae Borealis, showing blue-shifted absorption line accompanying each emission line. The nova evolved and they later observed a spectrum characteristic of nebula. These 'P-Cygni' lines are a characteristic common to all novae and stars with strong mass ejections or violent stellar winds such as Eta Carinae. The stellar 'ashes' that accumulate often take the form of a circumstellar nebula of gas and dust. In the late 19th century, Keeler discovered the unusual emission lines of P-Cygni, a variable star which may have had a novae phase in 1600. It had several bright lines ascribed to helium, and is now classified as a very slow nova. A quote from C.S.Beals paper on the interpretation of these stars: Both P-Cygni and Eta Carinae have been numbered among the novae ... This similarity with novae, considered in connection with the absorption on the violet edges of emission lines and the variation in the width of P Cygni lines with wavelength, suggest that the peculiarities in the spectra of these stars is due to the ejection of of gaseous material in a manner similar to that suggested for Wolf-Rayet stars. http://home.achilles.net/~ypvsj/news/EtaCarinae.html P Cygni emission line profile of triply ionized carbon at 1548.2 � in the central star of the cat's eye planetary nebula, NGC 6543. Courtesy of the International Ultraviolet Explorer (IUE). Huggins and Miller were the first to observe the spectra of nova T Coronae Borealis, showing blue-shifted absorption line accompanying each emission line. The nova evolved and they later observed a spectrum characteristic of nebula. These 'P-Cygni' lines are a characteristic common to all novae and stars with strong mass ejections or violent stellar winds such as Eta Carinae. The stellar 'ashes' that accumulate often take the form of a circumstellar nebula of gas and dust. In the late 19th century, Keeler discovered the unusual emission lines of P-Cygni, a variable star which may have had a novae phase in 1600. It had several bright lines ascribed to helium, and is now classified as a very slow nova. A quote from C.S.Beals paper on the interpretation of these stars: Both P-Cygni and Eta Carinae have been numbered among the novae ... This similarity with novae, considered in connection with the absorption on the violet edges of emission lines and the variation in the width of P Cygni lines with wavelength, suggest that the peculiarities in the spectra of these stars is due to the ejection of of gaseous material in a manner similar to that suggested for Wolf-Rayet stars.

53. 8/25/2012 Fl�vio Cruz / FI-196 53 Laser Safety Classifications Slide provided by Optics I student Kham Ho, 2004Slide provided by Optics I student Kham Ho, 2004