OPTI510R: Photonics. Khanh Kieu College of Optical Sciences, University of Arizona Meinel building R.626

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1 OPTI510R: Photonics Khanh Kieu College of Optical Sciences, University of Arizona Meinel building R.626

2 Important announcements Homework #2 is assigned, due Feb. 12 Travel to NSF Feb 26-27, pre-record lecture Mid-term exam on Feb 28 (open books/notes) Final exam on May 2 (tentative)

3 Fabry Pérot Interferometer

4 Fabry Pérot Interferometer

5 Sagnac Interferometer The sagnac sensor has the best sensitivity compared to other type of sensors.

6 Fiber Optics Gyroscope

7 Laser Gyroscope We can easily measure f beat with <1Hz precision. What would be the smallest rotation rate that we can measure using a ring Resonator with 1m radius?

8 There are many other interferometers Michelson Mach-Zehnder Sagnac Fabry-Perot Fizeau Twyman-Green Newton Nomarski

$Diffraction and Devices Diffraction Overcoming the diffraction limit Diffraction gratings Ruled grating Holographic$

9 Diffraction and Devices Diffraction Overcoming the diffraction limit Diffraction gratings Ruled grating Holographic grating Volume grating Applications Tunable laser Spectroscopy Laser stabilization Pulse compression Volume grating

$Diffraction Diffraction relies on the interference of waves emanating from$ $Diffraction can be explained by interference Diffraction of a laser beam$

10 Diffraction Diffraction relies on the interference of waves emanating from the same source taking different paths to the same point on a screen Diffraction can be explained by interference Diffraction of a laser beam through a small circular hole (Airy disk) Young's double-slit interferometer Wikipedia

$Diffraction and nature of light Need to be in the near field: Arago spot, Fresnel$

11 Diffraction and nature of light Need to be in the near field: Arago spot, Fresnel bright spot, or Poisson spot This experiment confirmed the wave nature of light! Wikipedia

12 Huygens Fresnel principle Near field and far-field diffraction Wikipedia

$Diffraction$ $diffraction$

13 Diffraction limit How to overcome the diffraction limit?

14 Overcoming the diffraction limit

15 Overcoming the diffraction limit nobelprize.org

16 STED: Stimulated emission depletion nobelprize.org

17 STORM: Stochastic Optical Reconstruction Microscopy nobelprize.org

18 STORM: Stochastic Optical Reconstruction Microscopy nobelprize.org

19 STORM: Stochastic Optical Reconstruction Microscopy nobelprize.org

$Diffraction Grating A periodic structure that diffracts light into different directions.$

20 Diffraction Grating A periodic structure that diffracts light into different directions. Grating can be flat, concave, convex and arbitrary shape HeNe laser incident on a diffraction grating showing zero, first and second order beams

21 Diffraction Grating

22 Diffraction Grating

23 Basic equations Monochromatic source White light

24 Blazed grating Need: how to concentrate all the lights into one order? Solution: make the grating of right triangles with a braze angle. By tilting the slit faces to the normal of incidence of the desired order, grating efficiencies >90% can be achieved Blazed grating

25 Diffraction in Nature CDROM and DVD Blue Morpho butterfly Fossil Ammonite Peacock feather Opal Bug eyes

ruling machine: Diamond milling Ruled grating High throughput and

26 Grating fabrication-ruled grating Formed by physically writing grooves on a reflective surface with a diamond blade mounted on a ruling machine: Diamond milling Ruled grating High throughput and efficiency Maximum groove density of g/mm Good in IR and far IR Expensive

27 Grating fabrication-ruled grating

28 Grating fabrication-ruled grating Measured at Littrow configuration

reflectivity Maximum groove density of 6000g/mm

29 Holographic grating Formed by interference lithography and etch Low stray light and dense groove spacing Lower reflectivity Maximum groove density of 6000g/mm Availability of non flat substrate Good in UV, short wavelength

30 Holographic grating Fringe locking controller locks the interference image to moving substrate by correcting stage error and interferometer phase error

31 Holographic grating Lightsmith transmission grating Excellent diffraction efficiency

32 Volume grating Diffraction efficiency ~99% Narrow bandwidth

33 Bragg mirrors , 2 / 2, 2 ) ( 2 d n n d n n c c k d n n d k B Constructive interference for two layers of a segment Bragg frequency

34 Fiber Bragg gratings Fiber laser reflector, filter, dispersion compensator

35 Fiber Bragg gratings High Power Fiber Lasers

36 Tunable Grating Microelectromechanical Systems (MEMS) spring comb drive actuator

$diffracted back along incident beam InAs/GaAs quantum dots laser Beam rotates as you$

37 Applications-Tunable laser Littrow configuration: light of desired wavelength is diffracted back along incident beam InAs/GaAs quantum dots laser Beam rotates as you tune!

38 Applications-Tunable laser Littman-Metcalf configuration: grating is kept at a fixed angle and a special mirror is rotated to tune the output wavelength. Output beam is aligned at grazing incidence with grating. First order diffracted beam is sent to retroreflector (mirror) that reflects beam back to itself. High efficiency for TM polarization (light polarized perpendicular to grooves). Output is the zeroth order reflected beam off the grating.

39 Applications-Laser stabilization

$planar diffraction grating more degrees of$ wavelength M1: collimating light source

40 Applications-Spectroscopy Czerny-Turner Configuration two concave mirrors and planar diffraction grating more degrees of freedom, good coma correction at one wavelength M1: collimating light source M2: focus disperse light from grating asymmetrical geometry

41 Applications-Spectroscopy

42 Applications-Pulse compression Provide normal dispersion Compressed pulse

43 Applications-Pulse compression Schematic diagram of a chirped pulse amplification system

44 Optics of periodic structures Photonics crystal!

45 Questions for Thoughts Can you come up with a better way to overcome the diffraction limit? Can you create a new optics company making diffractive devices? Why there is a strong polarization dependence in diffraction efficiency for metal-coated ruled gratings? A compact device providing adjustable GVD with low loss? A diffraction grating with 100% diffraction efficiency and broad operating bandwidth?

OPTI510R: Photonics. Khanh Kieu College of Optical Sciences, University of Arizona Meinel building R.626

OPTI510R: Photonics. Khanh Kieu College of Optical Sciences, University of Arizona Meinel building R.626 OPTI510R: Photonics Khanh Kieu College of Optical Sciences, University of Arizona kkieu@optics.arizona.edu Meinel building R.626 Important announcements Homework #2 is assigned, due Feb. 11 Mid-term exam