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Course Information

Professor: Dr. Charles Durfee

Office: Meyer Hall 330

Meeting Times:

class: M W 11:00-11:50 AM Berthoud Hall 205

lab: Th 9-11:50, Meyer Hall 263

Announcements

In case your lost, the presentations are in Alderson 368, 9-12 today!

10 November 2015: I forgot to mention in class yesterday that I'll be giving the physics department colloquium today at 4pm in the CTLM auditorium. I'll be talking about a number of applications of ultrafast lasers...

Designing laser beams for control of nonlinear ultrafast interactions with matter

When working with beams of ultrafast laser pulses (typically 20-100 femtoseconds long), we have the capability of reaching very high focused intensity with a modest amount of energy in the laser pulse. At high intensities, for example in the 10^12 - 10^14 W/cm2 range, the laser field can ionize atoms. This leads to a wide range of applications ranging from micro-machining to high-order harmonic conversion to soft x-rays. In this talk, I will describe how we can manipulate the propagation of the laser beams to optimize some of the nonlinear interactions. Controlling the angular dispersion of the frequency components of the beam leads to a number of interesting effects such as temporal focusing. This can be exploited to localize the laser intensity even for relatively large focal spots. This control of “spatial chirp” can also be extended to novel beam geometries, such as Bessel-Gauss and vortex beams. Another example of control of nonlinear processes is high-order harmonic generation (HHG) with two non-collinear beams. In a recent collaboration with colleagues at JILA in Boulder, we have demonstrated a new way to generate circularly polarized high-order harmonic light by overlapping of two counter-rotating circularly polarized ultrafast pulses.

9 November 2015: For the last problem of the homework, you can assume that the HR radius of curvature is 500mm and the laser wavelength is 1064nm. When I refer to "optimum" cavity length, I'm saying that we pick the cavity length that optimizes the beam size at the curved HR mirror. Since I am giving you that beam size, you can calculate the cavity length directly.

4 November 2015: Guidelines and ideas for the final project are posted below. Each person should come to see me during office hours to discuss a plan for what you will be doing for your project. I can help locate references and come up with ideas.

2 November 2015: HW 5 was posted on saturday, due a week from this wednesday.

We will be offering Physical and Fourier Optics next semester. Possible meeting times are: MW 3-4:15, 4:30-5:45 or TTh 12:30-1:45, 2-3:15, 3:30-4:45. Please let me know if you are interested, and also let me know if there are times you *cannot* make it.

Course summary:

This course will address topics related to the propagation of light through optical systems. Such an understanding is essential to being able to work with modern optical technology. Diffraction theory shows that the field distribution at the focal plane of a lens is the 2D Fourier transform of the field transmitted through the lens. This enables the use of linear systems theory (transfer functions, convolution) to describe imaging systems: microscopes, spectrometers, holography. We will also cover topics in ultrafast optics, waveguides, and beam propagation. To increase the utility of the course, we will use some numerical methods to be able to calculate beam propagation in complex systems.

Tentative syllabus: I'd like to also address topics in structured light imaging and super-resolution techniques.

Syllabus • 1D Fourier techniques with applications to ultrafast optics (t-ω domain) o Fourier transform techniques

  •	Shift, scale, modulation, convolution, etc.
  •	Application to intuitive analysis 
  •	Fourier transform spectrometers (FTIR)
  •	Temporal coherence

o Linear systems theory

  •	impulse response and transfer functions
  •	amplitude and phase filters
  •	Dispersive propagation, pulse compression

o Numeric techniques

  •	Sampling theory, FFT and numeric convolution
  •	Fourier split-step method applied to pulse evolution

o Advanded applications topics:

  •	Pulse shaping/synthesis, Gerchberg-Saxton optimization
  •	Pulse characterization
  •	Alternative representations of t-ω space – Wigner transforms
  •	Modeling nonlinear pulse propagation: pulse compression, soliton dynamics 
  •	Physical optics and wave propagation

o 2D Fourier transforms (spatial/spatial frequency domain)

  •	Cartesian coordinates: angular plane wave spectrum
  •	Cylindrical coordinates: Fourier-Bessel transforms

o Scalar diffraction theory

  •	Fresnel and Fraunhofer diffraction 
  •	Fresnel calculation of propagation of Gaussian and arbitrary beams
  •	Wavefront characterization techniques

o Modal decomposition

  •	Hermite-Gauss and Laguerre-Gauss beams 
  •	Vortex beam
  •	Bessel and Bessel-Gauss beams
  •	Waveguide modes: index guiding, surface plasmons
  •	Leaky modes

o Fourier split-step method applied to beam propagation

  •	Free-space propagation
  •	Applications: integrated optics, resonators, nonlinear beam propagation
  •	Spatio-temporal methods
  •	Imaging and holography

o Abbe imaging theory

  •	Frequency analysis of imaging systems (MTF, OTF)
  •	Spatial filtering and optical processing

o Microscope and imaging systems using Fourier techniques o Beam shaping

  •	Spatial light modulators and deformable mirrors
  •	Diffractive optics and phase plates

o Holography and spectral interferometry

22 October 2015: In-class midterm this coming Wednesday: 28 Oct. The subject matter will be what you've had homeworks on so far. See the study guide posted below in the homework section.

The solutions for the homeworks are available in my office for you to copy.

All lecture notes are up to date. The exact assignment of class number to actual lectures is approximate but the sequence is right.

8 October 2015: I just got back from my trip to DC, and I'm working in my office. I hope class and lab went well for you all. Feel free to stop by if you have any quick homework questions.

7 October 2015: The revised lab is posted - you should finish these this week. Remember the Sagnac interferometer is extra credit. Also, there are only two Fabry-Perot interferometers and you don't need to interfere with your other setup to use either one. So be sure to do that one when it's available.

5 October 2015: Posted slides for today and wednesday. They are bundled in the EMWaves and interference file.

2 October 2015: HW 4 is re-posted with 3 additional interference problems. This homework will be due Friday of next week. I will be out of town tuesday afternoon until thursday morning for a grant review meeting in DC. Mike Greco will be teaching in my place on Wednesday.

30 September 2015: Class notes and this week's lab are posted below.

29 September 2015: I posted the neon spectral data. As I posted it, I realized the file format will need to be converted to a tab delimited or .csv so other programs like Excel or mathematica can read it. Could someone read the .prospec file into the spectrometer software and do the conversion? When you do, email it to me and I'll post it.

Also notice the file that is there that describes the different transitions that participate in the neon inversion and the decay out of the laser termination state. This will help you interpret the changes in the emission spectrum from not lasing to lasing.

28 September 2015: As discussed in class, homework 4 will be due Oct 7. I will re-post it with some additional questions to account for the second week. In the meantime, I've posted a pdf of the current homework that has the figure for problem 1.

I have the solutions for HW1 and 2 printed out. They are available in my office if you'd like to look or make a copy.

27 September 2015: Homework 4 is posted.

22 September 2015: Homework 3 hints and tips: On the last problem, you need a value for the saturation fluence. Use 0.85 J/cm2, which is the saturation fluence for Ti:sapphire. I put this in an updated copy of the homework assignment.

21 September 2015: Homework 3 hints and tips: Problem 3: For both parts a and b, the central frequency is 10^14 Hz. I had it listed just for part b. If you need a refractive index for this problem, you can take n = 1. One way to approach this problem is to first find the Einstein coefficient B21 first.

Problem 4: For this, it is helpful to work with equations in chapter 2 to get a connection between the spontaneous emission rate and the cross-section that is independent of the dipole moment.

14 September 2015: Homework 3 is posted. This is due in 1 1/2 weeks, but of course getting started earlier is better.

4 September 2015: Homework 2 is posted. The file is in Mathematica format, since most of the problems can be done in that program.

2 September 2015: Lecture notes for Wednesday are posted: see below. Later I will rearrange the files so they reflect what we actually get to in each class.

31 August 2015: Lecture notes for Monday are posted: see below. I re-posted the slides just after class, to fix a couple of typos and to add a couple of figures. We got up through slide 17 today, but we'll review a bit in the beginning of class on Wednesday. Read through the slides, work through the missing steps, and bring your questions to class on Wednesday.

26 August 2015: Lecture notes are updated, and the lab for Thursday is posted below.

If you have a Windows laptop, please bring it to the lab.

You can load the software for the power meter using this website:

PM100 software

This should work for any version of Windows.

The camera software is at this site:

Camera software

This only works on Windows 7.

For later versions of Windows (at least 8), this driver should work. [1]

23 August 2015: Welcome to Laser Physics!

Office hours

Times: M12:30-3:00, W1:00-3:30

Let me know if you cannot make any of these office hours. I have monthly meetings on wednesdays, so the wednesday hours will occasionally shift to 1-4.

Look for me either in my office or in the advanced lab on the second floor.

Course Material

Syllabus and Reading List

Main text: O. Svelto, Principles of Lasers, 5th edition. It is available for purchase at the bookstore. There is also online access to the book from a campus/VPN connection:

http://www.springerlink.com/content/n72670/#section=672851&page=1

These downloads require Adobe Acrobat Reader

Course syllabus for 2015

Homework Assignments and Midterm:

Grading policy:

Turn in homework on time for full credit. At the time we give homeworks back to you, solutions will be available in printed form in a binder that I'll keep, but you can make a copy.

These downloads require Adobe Acrobat Reader

Homework 1 due by 5pm 2 Sept.

Homework 2 due by 5pm 9 Sept.

Homework 3 due by 5pm 23 Sept.

Homework 4 due by 5pm 9 Oct. New deadline, 3 additional problems on interferometry. Be sure to do the interferometry problems before Thursday's lab.

Homework 4 pdf version

Study guide for in-class midterm

Homework 5 due 11 Nov

Lab exercises:

These downloads require Adobe Acrobat Reader

Lab 1: optical alignment skills

Lab 2: HeNe gain and lasing

Lab 2: some background reading about HeNe lasers.

Lab 2: zip file containing .png picture of Neon spectrum and a spectrometer data file that needs to be converted to .csv or tab delimited.

Lab 3: interferometry. This version has another couple of exercises on Fabry-Perot and Fizeau interferometers.

Lab 4: HeNe resonator modes

Lab 4 and 5: HeNe resonator modes, labs 4 and 5

Final project

These downloads require Adobe Acrobat Reader

Final project guidelines and ideas

Lecture Notes

While these notes are primarily to help me give my lectures, I'm posting them to help you fill in things you may have missed in class or to show the details of calculations we don't have time to work through. If you have any constructive input on how to make these more useful to read, let me know.

Note: if someone would like to make use of these slides, please acknowledge me. I would be happy to share the original .pptx files on request (email).

2015-09-21: fixed some typos that gave extra e^2 factors in the classically-calculated spontaneous emission rate. Notes are updated.

This list is from 2015.

These downloads require Adobe Acrobat Reader

Class 1: introduction

Classes 2 and 3: waves, simple resonators and blackbody radiation

Class 4: Quantum Mechanics and transitions

Class 5: line shapes and cross-sections

Class 6: absorption and gain

Class 7: rate equations and Einstein A,B coefficients

Class 8: line broadening and saturation

Class 9: amplifier design

Class 10: EM waves revisited