The Optics Revolution

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Maximilian Flynn
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5 The Optics Revolution 1960 The beginning of the 20 th century optics renaissance Dawn of the optics revolution... Source: Han Le & Assoc

6 Photonics Component Development Detector Source Circuit, Processor Optical fiber photodiode Sem. laser Optical Fiber Laser Sensitivity, Speed: p-i-n Gain: APD SM laser Low noise Ultrafast Uniform array Long-life laser power laser Beginning of the "optical renaissance" Low loss waveguide Reliable WG mod. Opt. Amp Low noise Ultrafast TIA, ROIC electronics Photonics coming of age: the optocentric paradigm System laser The big bang of photonic circuit

INFORMATION TECHNOLOGY Charge of the Light Brigade 1/31/00 Next-generation optical gear is entering the local market Over the past year, optical-networking companies have become the darlings of the

7 INFORMATION TECHNOLOGY Charge of the Light Brigade 1/31/00 Next-generation optical gear is entering the local market Over the past year, optical-networking companies have become the darlings of the technology world The technology could be crucial in realizing the promise of the Internet. Optical technology has the potential to boost the capacity of telephone companies' networks a millionfold. ''You're not going to be a player in the next generation without optics, ' says Michael O'Dell, chief scientist at MCI WorldCom Inc.'s UUNet Internet unit. ''It's life and death. 1/2000

The Optical Internet and Telecom World 1999-2005: The

Amsterdam The Osaka optocentric paradigm shift London

Gbps Brussels Paris Milan Monaco Frankfurt Zurich Total

NETWORK - Mid 1999 US Domestic Backbone 268,794 OC-12

8 The Optical Internet and Telecom World : The quiet industrial revolution: Stockholm Seoul Tokyo Amsterdam The Osaka optocentric paradigm shift London Hong Kong Singapore Total Transatlantic Capacity is 3 Gbps Brussels Paris Milan Monaco Frankfurt Zurich Total Trans-Pacific Capacity is 500 Mbps Sydney UUNET GLOBAL NETWORK - Mid 1999 US Domestic Backbone 268,794 OC-12 Miles electrons in copper light OC-48 in fiber Basedoptic Source: Han Le & Assoc

9 Source: Michael Lebby US-OIDA Han Le & Assoc The Second Optics Revolution...

10 Link: From Japan OITDA

13 Optoelectronic Devices Light-to-current conversion: Photodiodes, photodetectors - p-i-n, (why need i?) dark current, I-V curves, photovoltaic current sources - APD, avalanche region, gain, multiplication factors Power devices: solar cells Current-to-light conversion: LEDs, lasers, optical amplifiers: Fluorescence, optical gain, stimulated emission, coherent radiation, threshold, efficiency Electric field/light interaction effects: Electro-optic modulator, electroabsorption modulator (LCD for example) Photonic circuits: light conditioning, manipulation structure

15 Optoelectronic Devices Light-to-current conversion: Photodiodes, photodetectors - p-i-n, (why need i?) dark current, I-V curves, photovoltaic current sources - APD, avalanche region, gain, multiplication factors Power devices: solar cells Current-to-light conversion: LEDs, lasers, optical amplifiers: Fluorescence, optical gain, stimulated emission, coherent radiation, threshold, efficiency Electric field/light interaction effects: Electro-optic modulator, electroabsorption modulator, (LCD for example) Photonic circuits: light conditioning, manipulation structure

16 Where is the depletion width?

17 ECE 6323

18 Introduction Fundamentals of laser Types of lasers Semiconductor lasers

19 Is it Light Amplification and Stimulated Emission Radiation? No. So what if I know an acronym? What exactly is Light Amplification and Stimulated Emission Radiation? Laser is a device that emits a special type of light source

Is it because it is collimated (goes as a straight and narrow beam?

20 Laser is a device that emits a special type of light.. What is so special this type of light? Is it because it is collimated (goes as a straight and narrow beam? Is it because it is bright? Is it because it has a single color? Is it because it is pretty? Well that depends what pretty is? Is it? NONE OF THE ABOVE! It emits COHERENT light!

21 Is it light that can speak in clear sentence and not drunk? Coherent light: the photons have the same phase, temporally, spatially. Temporal coherence Spatial coherence

22 Implications of coherent light on optical communication application Temporal coherence: can be made into short pulse with minimum bandwidth: transform-limited pulse Spatial coherence: can be focused into small spot (and still high power): diffractionlimited beam Laser is essential for efficient optical communication: short pulse in small space

23 Fundamental physics: stimulated emission and amplification of light: optical gain Materials and energy input: pump Device: optical amplifier Fundamental optics: optical cavity and optical modes Device: optical resonator Fundamental of laser physics: Lasing process Behavior, properties Laser engineering

24 Fundamental physics: stimulated emission and amplification of light: optical gain Materials and energy input: pump Device: optical amplifier Fundamental optics: optical cavity and optical modes Device: optical resonator Fundamental of laser physics: Lasing process Behavior, properties Laser engineering

25 Review of modern physics

26 Fundamental processes: Stimulated emission

27 Pumping and Spontaneous emission

28 Stimulated emission

29 Stimulated emission through a population

33 Principle of detailed balancing

34 The higher photon density (the more light) the higher the stimulated emission rate is compared with spontaneous emission: when P stim >> P spont : lasing occurs

35 Population inversion concept

36 Optical amplification Energy pump Pin P out P in P z P Pin N N ) z ( 2 1 dp dz gp If g>0: Optical gain (else, loss) Optically amplified signal: coherent with input: temporally, spatially, and with polarization

37 Media for optical amplification (and lasers) Gas: atomic, molecular Liquid: molecules, micro particles in a solution Solid: semiconductor, doped materials (EDFA)

38 Fundamental physics: stimulated emission and amplification of light: optical gain Materials and energy input: pump Device: optical amplifier Fundamental optics: optical cavity and optical modes Device: optical resonator Fundamental of laser physics: Lasing process Behavior, properties Laser engineering

39 Optical cavity

40 Why optical cavity is essential to the laser? Has only certain modes (and frequencies) Allows the structure to be a resonator when the input coincides with the modes Allows a self-oscillation solution without any input

41 Fundamental physics: stimulated emission and amplification of light: optical gain Materials and energy input: pump Device: optical amplifier Fundamental optics: optical cavity and optical modes Device: optical resonator Fundamental of laser physics: Lasing process Behavior, properties Laser engineering

42 Illustrative concept

43 Basic laser equation T1 T2 T2 0 l T1 rp2 2 l rp1 rm2 rp2 tm2 tp2 tm1 tm2 l l rm2 rp1 T1 tm1 tm2

44 A threshold: the pump power where the net gain after one round trip is equal to the total cavity loss. Above this, the laser emits laser radiation (not spontaneous emission) The output light has frequencies and spatial profiles that are the optical modes of the laser cavity There are two types of spatial modes: longitudinal modes determined by the cavity length, and transverse modes determined by the cavity lateral geometry. Each spatial mode is a combination of a longitudinal and a transverse mode. Likewise, there are polarization modes, and the combination of spatial and polarization modes determines unique modes. There is a unique frequency with each mode A laser may emit a single dominant mode (under certain pump power), which is called single-mode operation or single-mode laser. The ratio of the dominant mode power to that of all other modes is called side-mode suppression ratio. Otherwise, it is called multi-mode operation or multi-mode laser

45 Optoelectronic Devices Light-to-current conversion: Photodiodes, photodetectors - p-i-n, (why need i?) dark current, I-V curves, photovoltaic current sources - APD, avalanche region, gain, multiplication factors Power devices: solar cells Current-to-light conversion: LEDs, lasers, optical amplifiers: Fluorescence, optical gain, stimulated emission, coherent radiation, threshold, efficiency Electric field/light interaction effects: Electro-optic modulator, electroabsorption modulator, (LCD for example) Photonic circuits: light conditioning, manipulation structure

47 I op qg op L n L p W A total s qv/ k T e Iop B I I 1 What is g op? g op N photon

48 s op B PV s op T k qv op T k qv s total I I q T k V I I e I e I I B PV B PV / ln 1 / / /

49 Power = 0 Power = 0 Maximum power < 0

50 Current linearly proportional to light intensity: I total dark op qv/ kbt I s e 1 I I op RP P is optical power, R is defined as responsivity I I Key figure-of-merit: minimum detectable power (noise equivalent power); bandwidth op Detector link

51 Optoelectronic Devices Light-to-current conversion: Photodiodes, photodetectors - p-i-n, (why need i?) dark current, I-V curves, photovoltaic current sources - APD, avalanche region, gain, multiplication factors Power devices: solar cells Current-to-light conversion: LEDs, lasers, optical amplifiers: Fluorescence, optical gain, stimulated emission, coherent radiation, threshold, efficiency Electric field/light interaction effects: Electro-optic modulator, electroabsorption modulator, (LCD for example) Photonic circuits: light conditioning, manipulation structure

52 LCD

53 Optoelectronic Devices Light-to-current conversion: Photodiodes, photodetectors - p-i-n, (why need i?) dark current, I-V curves, photovoltaic current sources - APD, avalanche region, gain, multiplication factors Power devices: solar cells Current-to-light conversion: LEDs, lasers, optical amplifiers: Fluorescence, optical gain, stimulated emission, coherent radiation, threshold, efficiency Electric field/light interaction effects: Electro-optic modulator, electroabsorption modulator, (LCD for example) Photonic circuits: light conditioning, manipulation structure

$waveguide grating Diffraction G Other gratings Convent. fiber DSF, NZDSF Improved fiber Erbium-doped Fib. Amp (EDFA) Semicond.$

54 Optical/DWDM networking technology Transmitter WDMux Fiber Optical amplifier Laser -DFB, DBR, VCSEL -Tunable, fiber Modulator -Electro-optic -Electroabsorption TF filters Fiber Bragg G Array waveguide grating Diffraction G Other gratings Convent. fiber DSF, NZDSF Improved fiber Erbium-doped Fib. Amp (EDFA) Semicond. (SOA) Others (Raman) Optical switch Path switch Add/Drop mux l-router Cross connect Couplers circulators Receiver Ultrafast PD

Introduction Fundamental of optical amplifiers Types of optical amplifiers

ECE 6323 Introduction Fundamental of optical amplifiers Types of optical amplifiers Erbium-doped fiber amplifiers Semiconductor optical amplifier Others: stimulated Raman, optical parametric Advanced application: