PHTN1400
Principles of Laser Systems

(2012 Winter)

Course Description

The basic principles from PHTN1300 are applied in this practical course which examines the operating principles, procedures, maintenance, and applications of specific laser systems including gas (including ion, CO2, and excimer) and solid-state (including YAG and ruby) types. Power/pump sources, laser structure, cavity optics, basic laser processes, beam characteristics, and emission spectra for these lasers are examined. Specifics of wavelength selection (for multi-line lasers), pulse generation (including Q-switching and modelocking), and non-linear optics (harmonic generation and OPO) are included. Safety issues (e.g. laser classes and eyewear OD) will also be covered. A laboratory component allows students to investigate the operational principles of practical laser systems.

The output of our Innova-90 argon laser is seen here. Using multi-line optics several wavelengths lase simultaneously. The output beam is then split by a diffraction grating to reveal all the spectral components. As tube current is increased gradually more lines begin to appear - in this case the current is relatively low (< 20A) so only five lines are lasing. Clearly visible are the 488nm blue and 514nm green lines. This laser is used to demonstrate Mode structures (TEM_xx), wavelength selection, quantum principles (such as competition for energy levels), and ion laser hardware (e.g. power supplies and tube design). In multi-line, multi-mode operation it can produce seven watts of blue-green laser light.

A detailed description of the course can be found in the Course Outline (CO) and Teaching & Learning Plan (TLP) documents which can be found on Blackboard (for registered users only). The TLP contains a list of all topics covered.

Prerequisites

PHTN1300 Principles of Lasers & Light Sources
ELNC1320 ElectroTechnology II

This course is a prerequisite for PHTN1500 Advanced Laser Theory

You Are Here ...

This course is offered as part of the Photonics Engineering Technician (2 year) and Technology (3 year) Programs at Niagara College.

Evaluation ...

Three term tests valued at 20% each
TERM TEST #1 : In Class

Safety (Calculating OD of glasses, NHZ, laser regulations)
Quantum mechanics of shared levels (including questions from lab 1)
CW Gas laser power supplies and tube design (HeNe & Ion, Basic Electronics, Tube structure, Maintenance, Gas Issues)
Resonators, modes (FSR), cavity optics (including stability criteria), wavelength selection, etalons
CO₂ lasers, low-pressure design only (Electronics, optics, role of gases, including material from various presentations)
All material from labs 1 and 2
Chapters 3-5 (all background from PHTN1300), 6, 9, 11
Everything in "HeNe Lasers", "HeNe Case Study", "Ion Lasers", "SP Intro", and "CO2 Lasers Low Pressure" documents

TERM TEST #2 : In Class

TEA and Excimer lasers (including circuit design, discharge dynamics, E/P ratio)
E/P ratio in gases (including material from the presentation and labs)
Solid-State lasers (up to, but not including, Q-switching)
SS Lasers: Thermalization of LLLs and Gain calculations (from class)
SS Lasers: Pumping techniques, flashlamps/arc/diode
Q-Switching: Basics (Null buildup), AOM only (basic principles, bragg angle)
All material from lab 3
Chapters 3-5 (all background from PHTN1300), 10, 12
Everything in "E/P Ratio", "CO2 Lasers - TEA", "Pulsed Gas Lasers", and "Solid State Lasers" notes

TERM TEST #3 : In Class

Q-Switching and Modelocking (Fast-pulse techniques)
Q-Switches: Holdoff, threshold calculations
AO, EO modulators: calculations of %T
AOM/PCAOM: Bragg angle and DE computations
All material from lab 4 and 5

Labs and assignments valued at 40% total

Lab and Theory portions of the course must be passed separately in order to pass this course. Refer to the TLP document on Blackboard for details.

Check your Registration Status, Marks, and Lab Group Assignments here

Course Policies ...

NOTE: COURSE POLICIES HAVE CHANGED SINCE LAST YEAR ....

Course policies have been realigned to match the Standardized Policies and Procedures for CEE (dated January 2011). In summary, the changes for 2012 are:

LATE assignments are now worth ZERO. There is no longer a "grace period" with a "per day" penalty. Late submissions (i.e. ANY not printed and ready when you enter the lab) receive a mark of zero. You will be DENIED access to the printer at the start of the lab - either the lab is ready to submit, or it is late and hence worth zero.
Students are allowed only ONE single-day late submission without penalty. This is a once only one-day extension ... once used, any further late submission will receive an automatic zero.

(This policy reflects expectations in the real world: to be late for work, once, will likely not result in termination however chronic late arrivals will almost certainly result in job loss. Develop good work ethic _now_.)

Students must pass the theory (testing) and practical (lab/assignment) portions of the course separately in order to receive a passing grade. If a failing grade is received in either portion, then the lower of the two marks (theory or practical) will become the final grade.
In order to be considered for supplementary evaluation (SE) upon failure in this course, a mark of 50% minimum will be required in the practical (lab/assignment) portion of the course plus a mark of 45% minimum in the theory (testing) portion. A theory mark of 44% or less, or a lab mark of 49% or less, will result in failure with no SE option.
The SE procedure in this course is an extensive assignment followed by an all-encompassing exam. Only upon successfully completing the assignment (a minimum mark of 80% is required) will the exam be scheduled.

Complete course policies can be found in the Teaching and Learning Plan (T&LP) document found on Blackboard (for registered users only).

Textbook

Fundamentals of Light Sources and Lasers by Csele, 2004, John Wiley & Sons, ISBN 0-471-47660-9

Chapters 6 through 15 are covered in this course.

Supplemental Text: The Laser Guidebook, 2nd edition (or newer) by Hecht, McGraw-Hill, 1992, ISBN 0-8306-4274-9

For specific elements of this course, refer to both the Course Outline (CO) and the Teaching & Learning Plan (TL&P) documents, both available on Blackboard.

Students will use a Crystal Technologies AO Modulator in the laboratory to examine both Bragg and Raman-Nath regimes. Here a HeNe beam is diffracted by the modulator.

Course Notes

Classroom Presentations and Links to Augmenting Material:

Pre-lab Material ...

Standard Operating Procedures (SOPs) for lasers in Niagara College's high powered laser labs.
Laser Safety For Students from the in-class presentation.
Coherent.Com where you may download the laser safety video shown in class. Also, some manuals for our Coherent lasers are available here.

Watching this video, and writing a quiz BEFORE the first lab is MANDATORY!

CW Gas Lasers ...

Entrance Exam Solution useful for identifying areas requiring academic attention. (The examination was given last term).
Helium-Neon Lasers from the in-class presentation. Covers HeNe lasers and wavelength selection via optics.
HeNe Gas Laser - Case Study outlining issues such as competition for ULL (good prep for the term test).
Ion Lasers from the in-class presentation. Covers Ion lasers as well as longitudinal modes, linewidth, and use of etalons. (Updated 2012/01/25)
Ion Lasers - A Summary from a Spectra-Physics manual. A good overall review of ion lasers.
A few links for the unit on ION LASERS:
- History of Gas Lasers from Optics & Photonics News published by the OSA (must be opened from a college computer).
- Sam's Laser FAQ on Ion Lasers including discussions of gas pressure issues ("spectral balance") in Ar⁺ and Kr⁺ lasers
CO2 Lasers - Low Pressure primarily covering quantum mechanisms of the CO2 laser as well as design of CW lasers.
A few links for the unit on CO2 LASERS:
- Sam's Laser FAQ on Homebuilt CO2 Lasers including discussions on optics

Pulsed Gas Lasers ...

E/P Ratio covering design issues with nitrogen, excimer, and CO₂ gas lasers.
E/P Graph allowing determination of the E/P ratio for nitrogen gas.
CO2 Lasers - TEA primarily covering E/P issues, preionization, and discharge circuit design.
Pulsed Gas Lasers primarily covering Excimer and Nitrogen lasers and discharge circuit design.

Solid-State Lasers and Q-Switching...

Solid State Lasers the in-class presentation. (Password protected PDF).
Pre-Requisite (Review) Material for Solid-State Lasers, Q-Switching, and Midterm #2 ...
- Laser Gain from the in-class presentation (the most important concept from last term!) (Password-protected PDF). Contains an example question about Q-Switch holdoff which is an excellent introduction to Q-Switching.
- Cross-Sections and Gain from the in-class presentation (the second most important concept from last term!) (Password-protected PDF). Contains an example question pertaining to computation of inversions and thermalization of the LLL.
Q-Switching (Password protected PDF)
Harmonic Generation Password protected PDF file.
Dye Lasers Password protected PDF file.

General Notes:

Notes on Lab Reports a tutorial on writing formal lab reports.
Notes on Lab Reports, Part 2 a tutorial on writing condensed lab reports.
Midterm #1 Preparation Questions a selection of example questions from previous midterm examinations as covered in class (solutions done in review class). Password protected PDF file.
Final Review Questions from a previous review class.
Final Exam Material a checklist of all concepts listed in the CIS and considered "fair game" for the final exam.
Final Exam Review Questions a host of questions from various sources as practice for the final exam.
Final Exam Formula Sheet a typical formula sheet from a previous exam.

Reading List: (Scientific American Amateur Scientist Articles available on CD in the library or from L-18 for sign-out)

September 1964 How a Persevering Amateur Can Build a Gas Laser in the Home (HeNe Laser)
December 1965 Deep Sky Photographs with a 35-Millimeter Camera and More about the Homemade Laser (Follow-Up to the above article)
October 1980 A Homemade Mercury-Vapor Ion Laser That Emits Both Green and Red-Orange (Hg⁺ Laser)
Feburary 1969 How to Construct an Argon Gas Laser with Outputs At Several Wavelengths (Ar⁺ Laser)
June 1974 An Unusual Kind of Gas Laser That Puts Out Pulses in the Ultraviolet (N₂ Laser)
Feb 1970 A Tunable Laser Using Organic Dye Is Made At Home for Less Than $75

Laboratory Assignments

Students in 2012W will complete five laboratory assignments, each two-weeks in length. Lab sections are split into smaller groups (A and B) which perform different parts of the lab alternatively.

NOTE: You will NOT be permitted into the lab and will be marked absent unless the safety quiz on Blackboard has been successfully completed by the day before the beginning of the first lab

Lab #1: Safe Operation of Lasers (NEW for 2012)
The safe operation of lasers is examined including use of high-powered ion lasers. In the lab, the concept of Nominal Hazard Zone (NHZ) and optical density (OD) will examined with respect to correctly choosing safety glasses for specific lasers. The operating procedures of large ion lasers will also be demonstrated including use of current and light regulation modes, optics changes, and procedures to maintain a laser such as this.
WARNING:
  Safety Quiz on BLACKBOARD is due BEFORE admission to this lab. NO EXCEPTIONS: NO SUCCESSFUL QUIZ, NO LAB ADMISSION (And a mark of ZERO will result)
Lab Sessions:
  Section 01 (Mon), 02 (Thurs), & 03 (Fri) ...
  Group A - Part A during the week of 2012/01/23, Part B during the week of 2012/01/30
  Group B - Part B during the week of 2012/01/30, Part A during the week of 2012/01/23
  All Sections DUE during the week of 2012/02/06 (at the beginning of the lab)

Lab #2: Cavity Alignment
Complete alignment of the optics of two types of lasers will be completed. First, the optics on a large-bore MPB IN-100 carbon-dioxide laser will be aligned using a coaxial HeNe laser beam. Burn patterns will then be used to analyze beam structure under optimized and non-optimal conditions. Next, the optics (HR, OC, and Fold Mirrors) on a Coherent argon-ion laser-pumped dye laser will be removed and aligned by using the fluorescence of the dye itself to provide alignment 'spots'. A lab report will outline details of the procedure.
Lab Sessions:
  Section 01 (Mon), 02 (Thurs), & 03 (Fri) ...
  Group A - Part A during the week of 2012/02/06, Part B during the week of 2012/02/13
  Group B - Part B during the week of 2012/02/13, Part A during the week of 2012/02/06
  All Sections DUE during the week of 2012/02/20 (at the beginning of the lab)

No Lab on Week of March Break

Lab #3: Pulsed Gas Lasers
Students will mix various gas fills for a Lumonics Excimer 500 and a Lumonics TEA-203 CO₂ laser in V15 and will study the effect on power output. In the excimer laser, a Helium-Nitrogen mixture will be employed with various concentrations of nitrogen (the active lasing species) and the effect of nitrogen concentration on output power noted. In the TEA laser pressure and voltage will be varied. Results will be correlated with the calculated E/P ratio of the gases employed.

Lab #4: Q-Switched Lasers
A Diode-Pumped Lee YAG Laser employing an AO Q-switch will be examined with the effect of pulse rate on output determined. In order to demonstrate how an AOM works and ways in which it may be used an external AOM will be aligned for Bragg diffraction, with the effective intra-cavity loss determined, and an AOM modified for use as a PCAOM will be used to separate the multiple wavelength (RGB) output of a 'white light' HeCd laser.

Lab #5: DPSS Lasers (UPDATED for 2012)
Factors affecting stability in a DPSS laser are investigated. Using an argon-laser pumped tunable titanium-sapphire (Ti:Saph) laser, a vanadate laser will be pumped and the effect of pumping at various wavelengths examined. This unique "Laser-pumped-laser-pumped-laser" arrangement allows a regular DPSS laser to be pumped by a tunable IR source allowing investigation of the sensitivity of vanadate to pumping wavelength. The temperature sensitivity (for phase-matching) of KTP frequency doubling crystals is also investigated in this lab.

The lab schedule is subject to change based on availability of laboratory equipment

Contacts:

For the undergrad Photonics program ...
Program Coordinator Jay Yatulis
Office: V14
Telephone (905) 735-2211 x.7633
E-Mail: (Be sure to include 'Photonics' in the subject line to avoid deletion by an anti-spam filter)

For this course ...
Professor Mark Csele
Office: L-17 (Office hours are POSTED on the EL panel on the door)
Telephone: (905) 735-2211 x.7629
E-Mail: (Be sure to include 'Lasers' in the subject line to avoid deletion by an anti-spam filter)
URL: http://technology.niagarac.on.ca/people/mcsele

Copyright (C) Mark Csele and Niagara College, Canada, 2005-2012
Some images and text are published in Fundamentals of Light Sources and Lasers by Csele, Wiley (2004), ISBN 0-471-47660-9 and hence are Copyright (C) John Wiley and Sons. Further reproduction in any form is prohibited without written approval from the publisher.
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PHTN1400Principles of Laser Systems