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1、1.4 Laser characteristics,spectrally broad divergent cant be focused tightly not very intense incoherent,very monochromatic does not diverge as fast can be focused tightly can be extremely intense spatial coherence (interference) temporally coherent (beat notes),What is needed ?,More generally: gain
2、 medium pump - far from thermal equilibrium feedback (resonator, mirrors, cavity),發(fā)散,非相干,單色,干涉,反饋（諧振器，鏡子，腔）：光束的選擇性,增益物質(zhì)（激活物質(zhì)）：單光,泵浦源（激勵源）：粒子數(shù)反轉(zhuǎn),1897年發(fā)明法布里珀羅空腔諧振器,20世紀(jì)50年代中期，肖洛與美國著名物理學(xué)家湯斯共同研究微波激射問題。 當(dāng)湯斯提出受激輻射放大原理時，肖洛第一個提出運用沒有側(cè)壁的開放式法 布里-珀羅腔作振蕩器的設(shè)想。1960年，他和湯斯研制出第一臺激光器。,Fabry-Perot Etalon,增益飽和，粒子數(shù)不再反轉(zhuǎn)的時
3、候,,Gain? 當(dāng)受激輻射超過受激吸收和自發(fā)輻射的時候，即粒子數(shù)發(fā)生反轉(zhuǎn),固體（氣體、液體）增益物質(zhì)：三能級，四能級 半導(dǎo)體增益物質(zhì)：直接帶隙，間接帶隙,Loss：損耗,,簡稱開腔，全稱：開放式光學(xué)諧振腔,共軸球面腔：穩(wěn)定腔、不穩(wěn)腔、臨界腔，,*不同分子、原子及半導(dǎo)體材料中的電子有不同的E，其中半導(dǎo)體材料的E可變范圍很大,Different types of lasers,Free electron laser, UCSB (63 mm 2.5 mm),VCSEL array: vertical cavity surface emitting laser (850 nm),Ti:Sapphi
4、re laser: ultrashort pulses (30 fs) (700-1000 nm),Laser characteristics II -Threshold,,,kink in output power,spectral narrowing,線寬壓縮（線寬變窄）,扭結(jié)、彎曲,Laser history,,1910,1920,1930,1940,1950,1960,1970,1980,1990,2000,,,,,,,,,,,Lasers in science- ,laser cooling and trapping,interferometry length measurement
5、s,,biological processes,ultrafast phenomena,,Lasers in medicine- ,corrective eye surgery,removing blemishes,gallbladder surgery using fiber optics,Lasers in every day life,barcode scanners http://www.barcode-,laser printers,laser cutting laser welding ....,CD players,barcode scanners http://www.barc
6、ode-,,,電吸收分布反饋,Lasers in communication systems,光功率放大器,De-Multiplexer 分路器,Wavelength Division Multiplexer 波分復(fù)用系統(tǒng),前置放大器,Erbium-doped Optical Fiber Amplifer 摻鉺光纖放大器,隔離器,隔離器,耦合器,Energy Lever of Er3+,980 nm,1550 nm,1550 nm,1550 nm,1550 nm,Chapter 7 Some Specific Laser Systems,Solid laser,Gas laser,Excime
7、r laser （激基分子激光器）,Semiconductor laser,,Ruby Laser,Nd3+:YAG Laser,Neodymium-Glass Laser,,He-Ne Laser,CO2 Laser,（摻鉺光纖放大激光器）,,Quantum Well Laser,DFB Laser,VCSES Laser,,Gain Material,(EDFA),量子阱,分布反饋,垂直腔表面發(fā)射半導(dǎo)體,Fiber Laser,1.5.1,1.5.2,1.5.3,1.5.4,Active medium: Impurity ions in a transparent dielectric h
8、ost ions: rare-earth ( 3+) or transition-metal ions ( 3+) concentrations: 0.110% Hosts: crystals (oxides, garnets 石榴石or fluorides 氟化物) or glasses Pumping: optical pumping, Solid laser,(1) Ruby Laser,Ions: rare-earth (Cr 3+) concentrations: 0.05%, Hosts: Al2O3 (synthetic sapphire, 人造藍
9、寶石) First laser (1960); 3-level laser; pulse operation Optical Pumping: flashlamps ( 510-4 s) ( two absorption bands),See Figure 7-4, 692.5nm, R2 694.3nm, R1,See Figure 7-5,,（螺旋狀的）,,Typical setup of a pulsed ruby laser,(1) Ruby Laser,+ Circuit + Cooling system,Structure,(1) Ruby Laser,Paramete
10、rs: t flash t 2 N0 : N1 +N2 N2 :the number of atoms pumped into level 2,Applications: Holography （全息） Medical applications Large holograms Holographic interferometry Plasma diagnostics (等離子體診斷學(xué)） Comments: requires strong pumping long upper-state lifetime double pulse cooling problems
11、 low pulse rate poor efficiency,,Optical flux; Absorb coefficient; Absorb quantum efficiency;,(2) Nd3+:YAG pulse or CW operation (lower threshold) ; pulse operation,Four-level laser,See figure 7-9, Figure 7-10,Structure,Pumping,(2) Nd3+:YAG CW or pulse operation,3 relative motion,Total energy of
12、the molecular:,Figure 7-17, Energy level,(2) CO2 Laser,He: buffer gas,4 types of Construction:, Closed discharge tube, wave guide,(2) CO2 Laser, slow axial flow fast axial flow, transverse flow + transverse discharge transverse excitation atmosphere pressure,(2) CO2 Laser,More power with gas circu
13、lation （循環(huán)）,(2) CO2 Laser,Applications: Material processing Cutting and welding （焊接）of metals and non-metals Heat treatment of metals Scribing （雕合） Medicine no bleeding （止血） surgery ( water absorbs well in 10um) Research Spectroscopy (LIDAR) Laser chemistry Pumping of FIR laser Military,(3) Ion lase
14、r: Ar+ Laser,Visible( 350nm 520nm ), the most important laser Gas: Ar+ (18) or Kr+ (36) Pumping: electric discharge (電子放電） 4-level laser; CW operation,(3) Ar+ Laser,(3) Ar+ Laser,Advantages: high power in blue materials typically more sensitive for blue than for red good quality output beam and long
15、 coherence length Applications: Laser printers CD-ROM mastering Holography Spectroscopy Pumping of other lasers Surgery (eye) photochemistry Light shows,(4) Excimer laser,excimer (激基分子）= excited dimer （二聚物）,Structure:,Parameters:,(4) Excimer laser,(4) Excimer laser,Applications micromachining by laser ablation (polymers, biological materials, etc.) comeal sculpting (PRK, LASIK) photolithography （影印平版術(shù)） dye laser pumping,（消融，切除）,Pulsed Nd3+:YAG Pulsed CO2 Excimer laser, EDFA,
《激光原理與激光器》PPT課件.ppt
