Undergraduate Laser Laboratory at SJSU

Ken Wharton

SJSU Physics Department

• 4 of 14 full-time faculty members with laser/optics research background

• Houses “Institute for Modern Optics” (contact rdbahuguna@aim.com for more info)

• Located in the heart of Silicon Valley

Instead of a typical “Advanced Laboratory”, our department instead offers an optics laboratory and a laser laboratory for our upper-division majors.

Laser Laboratory: Overview

• 4 optical tables; 8 students/section

• 4 hours/week (2 units)

• No write-up time in class

The first few labs are identical for

all students.Then the students rotate through two sets of four labs.

Introductory “Experiments”

• Labs 1 & 2 (same for all students):– Laser and Electrical Safety– Mounts/hardware (built from scratch each week)– Optics handling/cleaning– Beam pointing + centering (HeNe laser)– Power measurements (HeNe laser)– ND Filters/Attenuation (Only actual experiment)– Scientific Writing Techniques

Need 4 sets of everything in these labs. (Optical Tables, ND Filters, power meters,

HeNe lasers, mirrors, hardware...)

Primary Experiments

• Align HeNe cavity; current vs. power (*)• Polarization Lab (/2, /4 plates, Pockels cell)• CCD Lab, Gaussian Beam Propagation• Photodetector response time (chopped HeNe)• He-Ne Beam Amplification / Saturation Intensity (*)• CO2 laser (homemade system) (*)• Argon-Ion laser (multi-line, diffraction grating expt.)• Interferometry (index of refraction of air)

Donated equipment includes CCD camera, optical tables, power supplies, HeNes, Optics, Hardware...

HeNe Discharge Tube

1st experiment: Use reference HeNe to align mirrors,optimize power output, plot discharge current vs. power.

2nd experiment:

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Increasing input power lowers gain (from ~15% to ~5%)allowing estimation of saturation intensity for HeNe.

CO2 Laser Experiment

• One mirror fixed; one mirror adjustable (students align with reference HeNe)

• Maximum power ~ 500mW

• Students try different output couplers

• Beam size estimated from burn spot on paper

• Students compute gain coefficient, efficiency

Final Thoughts

• Lab complements laser course– Usual reasons: Hands-on learning, etc...– The real world vs. 1st-order laser theory

e.g. Gaussian Beam Lab, introduce M2≠1– Lab experience key for jobs in photonics

• If interested in more info, please contact me:– Ken Wharton, wharton@science.sjsu.edu

Thanks: Sarma Lakkaraju, Kiumars Parvin, Ramen Bahuguna, Jose Garcia