Case Study: Laser Energy - Due urgently

Week 5 case study

Laser energy and power

Introduction

Lasers are common technology used in a wide range of applications. A laser pulse is composed of a packet of photons all with a similar wavelength and frequency traveling at the speed of light. The energy of each photon in the laser pulse is given by the following formula:

where h = 6.63x10-34 J*s (called Planck’s Constant)

In this case study, you will employ this formula, the speed of light, and the concept of power to determine the properties of a specific laser. To get started, review the following example:

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Example

A laser is used in eye surgery. The laser wavelength is 514.5 nm and it's Pulse Power is Ppulse = 1.5 Watts in each laser pulse. During the surgery the laser is pulsed for a time duration of 50 ms

During that pulse how many photons are produced?

The laser wavelength is given. We want to find the frequency first

.

The energy of each photon.

=

The Energy of the pulse is defined by the product of the pulse power and the time so

Then the energy of each pulse is ,075 Joules. The number photons n is:

17 is the number of photons produced in this pulse.

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Exercise

Now that you’ve reviewed the example above, it is time to explore the properties of a different laser. Review the case below and answer the questions that follow. Please show all your work below for full credit.

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A surgical laser with a wavelength of 810 nm delivers 250 mW of power on the retina of a patient. It produces a 1.5 msec duration pulse of light.

1. What is the energy of each photon? (30%)

2. What is the laser energy per pulse? (30%)

3. How many photons does it produce? (30%)

4. In what region of the spectrum is this light? (10%)