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2 LASER Light Amplification by the Stimulated Emission of Radiation ( 빛의증폭 ) ( 자극방출 )

4 평형상태에서 흑체복사에대한식 자극방출의자발방출에대한비 Einstein 계수

5 [ 예제 ] 온도 2,000K 에서작동하는텅스텐필라멘트의경우자발방출과자극방출의비를구하라. 필라멘 트에서발생하는빛의평균파장은 600nm 이다. 태양의표면온도가약 6,000 인점을생각하면아주높은온도이다. [ 예제 ] (a) 발생하는파장이 600nm 의경우어떤온도에서자극방출과자발방출이동일하게일어나는가? (b) 상온에서자극방출과자발방출이동일하게일어나는파장은얼마인가? (a) 빛은자발방출에의해발생하고, 자극방출은거의일어나지않는다. (b)

7 자발방출과자극방출로만들어진빛의차이점

8 자극방출의조건 항상 (always) 밀도반전 (population inversion) 상태가존재해야한다

9 4- 준위레이저의발진원리

10 공명기

11 레이저의구성요소

12 레이저빛의특징 1. 직진성 : 쌍둥이빛이방출 2. 단파장성 : 두활동에너지준위만관련

14 In 1917, Einstein proposed the process that makes lasers possible, called stimulated emission. In 1954, Townes demonstrated the first maser. The ammonia maser, the first device based on Einstein s predictions, obtains the first amplification and generation of electromagnetic waves by stimulated emission. Wavelength: 1cm, Power: 1nW In 1955, Nikolai Basov and Alexander Prokhorov attempted to design and build oscillators. The pumping method. In 1956, Nicolaas Bloembergen developed the microwave solid-state maser. In 1960, Theodore Maiman, constructed the first laser using a cylinder of synthetic ruby,1 cm in diameter and 2 cm long.

15 In 1960, Ali Javan, William Bennett Jr. and Donald Herriott developed the helium-neon (HeNe) laser, the first to generate a continuous beam of light at 1.15 μm. In 1962, Nick Holonyak Jr. published his work on the visible red GaAsP (gallium arsenide phosphide) laser diode. Red LED. In 1963, Herbert Kroemer (US) and Rudolf Kazarinov and Zhores Alferov(Russia) independently proposed ideas to build semiconductor lasers from heterostructure devices. In 1964, William Bridges discovered the pulsed argon-ion laser. In 1964, The carbon dioxide laser was invented by Kumar Patel. The most powerful continuously operating laser of its time, it is now used worldwide as a cutting tool in surgery and industry.

16 In 1964, The Nd:YAG (neodymium-doped YAG) laser was invented by Joseph Geusic and Richard Smith. LASIK, Skin resurfacing. In 1965, Jerome Kasper and George Pimentel demonstrated the first chemical laser, a 3.7-μm hydrogen chloride instrument. In 1967, Bernard Soffer and Bill McFarland invented the tunable dye laser. In 1970, Basov and Yu. Popov developed the excimer laser. In 1970, Alferov s group produced the first continuous-wave roomtemperature semiconductor lasers. In 1972, Charles Henry invented the quantum well laser. Holonyak first demonstrated the quantum well laser in 1977.

17 In 1976, John Madey demonstrated the first free-electron laser. In 1982, Peter Moulton developed the titanium-sapphire laser. Short pulses in the picosecond and femtosecond ranges. This laser replaced the dye laser for tunable and ultrafast laser applications. In 1994, Nikolai Ledentsov demonstrated the first quantum dot laser. In 1996, Wolfgang Ketterle demonstrated the first pulsed atom laser. In 1997, Shuji Nakamura, Steven DenBaars and James Speck announced the development of a gallium-nitride (GaN) laser that emits brightblue-violet light in pulsed operation.

18 레이저관련노벨물리학상수상자들 연도수상자업적 1964 Townes, Basov, and Prokhorov 최초의 Maser 발진 1966 Alfred Kastler Optical pumping 1971 Gabor Holography 1981 Schawlow and Bloembergen Laser spectroscopy 1997 Chu, Claude Cohen-Tannoudji and William Phillips Laser Cooling 2000 Kroemer and Alferov Semiconductor Lasers 2001 Cornell, Wieman, Ketterle Atom laser Bose-Einstein condensation 2006 Glauber Optical Coherence 2009 Charles Kao Optical Fiber Laser Communication

19 1953 년 stimulated emission in a stream of energized ammonia molecules to produce amplification of microwaves at a frequency of about 24.0 gigahertz Charles Hard Townes ( ) Nobel Prize in Physics 1964 with Nikolay Basov and Alexander Prokhorov. [

20 Ruby Laser First visible light LASER

21 Ruby Laser (1960) Theodore Maiman ( )

22 Energy Level of Cr 3+ in Ruby

23 Semiconductor Laser

24 Robert Hall ( ) -demonstrated the first semiconductor laser (GaAs) -Invention of a magnetron

25 Herbert Kroemer (1928- ) Zhores Alferov (1930- ) 2000 년 : Nobel Prize for developing semiconductor heterostructures used in high-speed- and opto-electronics

28 혼합물질 파장영역 GaAs 870nm GaAlAs 750~850nm AlGaInP 650~680nm InGaAsP 1.1~1.65 m InGaAsSb 1.7~4.3 m GaN 450~525nm PbSnTe 6~25 m PbEuSeTe 2~4 m

30 He-Ne Laser

31 William Bennett, Ali Javan : Helium-neon laser (1962 년 ) first gas laser -first laser to operate continuously, rather than in pulses. -A few years later Kumar Patel developed the CO2 laser.

32 Energy Levels of He and Ne Atoms

35 Dye Laser Dye 의형광스펙트럼

36 Peter P. Sorokin ( ) Fritz Peter Schäfer ( ) 년

37 Dye 분자의에너지준위

38 Dye Laser 의구조

40 Argon Laser William B. Bridges (1934- ) Inventor of Argon laser (1964)

43 Chandra Patel (1938- ) Inventor of CO2 Laser (1964)

46 Nd-YAG (neodymium-doped yttrium aluminium garnet) Nd:Y 3 Al 5 O 12 -first demonstrated by J. E. Geusic et al. at Bell Laboratories in 1964

47 형태파장출력형태 He-Ne nm ( 붉은색 ) 0.1~50 mw연속 10.6 μm ( 원적외선 ) 3~100W 연속 기체 337 nm ( 청색 ) 1~300 mw펄스 Ar 이온 488 nm, nm 5 mw ~20W 연속 ArF(excimer) 193 nm ( 자외선 ) 10W( 최고 ) 펄스당평균펄스 액체 색소 400~900 nm ( 색소종류에따라 ) 20~800 mw연속 / 펄스 ( 튜닝가능 ) Nd:YAG μm 0.04~600W 연속 고체 Nd:glass 1.06 μm 0.15~100J 펄스 반도체 (GaAs) 780~900 nm 1~40 mw연속 / 펄스

48 레이저의응용 1. 레이저빛에너지의직접적이용 - 레이저빛의직진성 - 물질의절단, 용접, 구멍 2. 정보, 통신에의이용 - 레이저빛의단파장성이용 - 음성, 영상신호를빛에실어서보냄

49 레이저의종류파장영역출력용도 엑시머류 Argon Fluoride Kripton Fluoride 193nm( 자외선 ) 248nm( 자외선 ) -절단, 녹임펄스형 -선택적세포응결펄스당평균 10W까지 -기타 Argonfp이저의적용분야 -근시교정 - 光응고 ( 망막 ), 접합, 증발 -안과수술( 망막 ) Argon-Ion 488nm( 청록색 ) 연속형 10W 까지 -외과수술용레이저메스 -레이저내시경, 응고장치 -코의연골절개및구멍 -모반, 오점, 문신제거 색소 (Dye) (Argon-ion 으로펌핑 ) 631nm( 적색 ) 연속형 3-4W - 光활성 ( 종양치료 ) - 내시경을사용한선택적응고 Nd:YAG 1.06 m( 적외선 ) CO m( 적외선 ) Ruby 694.3nm( 적색 ) 연속형 W까지연속형 80W까지펄스형펄스당 J - 光응고, 증발, 절개, 구멍 -외과수술용레이저메스 -레이저내시경, 응고장치 -조직증발, 절개 -외과수술용레이저메스 -의료용으로가장널리사용 -충치, 치석제거 -구강종양등치과용으로사용

57 LASIK (Laser Associated Stromal Insitu Keratomileusis) 1990 년 Pallikaris 박사가고안 엑시머레이저수술 (PRK) 과 미세각막절제술 (keratomileusis) 을혼합

59 Lasik 과정

60 Laser 의응용

61 비염, 축농증수술

62 반점제거 ( 레이저탈색 )

63 혈관의막힘을레이저로뚫음

64 혈관의막힘을레이저로뚫음

66 레이저메스

67 충치레이저치료

68 Optical Fiber

71 n 2 n 1 굴절의법칙 n 1 sinq 1 =n 2 sinq 2 n 1 >n 2 전반사임계입사 : n 1 sinq c =n 2 sin90 0 q c =sin -1 (n 2 / n 1 )

73 [ 예제 ] 굴절율이 1.5 인유리섬유의표면에굴절율 1.42 인물질로입혔다. 이유리섬유의단면에빛을입사할때전반사가일어나는최대의입사각도 는몇도인가?

75 Sir Charles Kuen Kao (born 4 November 1933) Father of Fiber Optic Communications 2009 Nobel Prize in Physics for "groundbreaking achievements concerning the transmission of light in fibers for optical communication

레이저의 종류

레이저의 종류 레이저의종류 이병호서울대전기공학부 byoungho@snu.ac.kr 레이저의종류 매질의종류에따라고체 : 루비레이저, Nd:YAG 레이저, Ti:Sapphire 레이저, 광섬유레이저, 기체 : 탄산가스레이저, 헬륨 - 네온레이저, 아르곤이온레이저, 엑시머레이저, 기타 : 색소레이저, 자유전자레이저 발진종류에따라연속파 (cw: continuous wave) 레이저펄스레이저