High-Power Pulsed Fiber Laser - Revision history

Wikiuser: file name correction and minor formatting changes

2014-08-25T04:19:08Z

file name correction and minor formatting changes

Wikiuser: Addition of Power curve measurements and figures

2014-08-25T04:16:30Z

Addition of Power curve measurements and figures

Wikiuser: Uploaded several more figures

2014-08-25T04:07:31Z

Uploaded several more figures

Wikiuser: most photo's uploaded

2014-08-24T18:49:13Z

most photo's uploaded

Wikiuser: figure testing

2014-08-24T18:46:28Z

figure testing

Wikiuser: Testing figure uploads

2014-08-24T18:20:18Z

Testing figure uploads

Wikiuser: formatting changes

2014-08-24T18:08:28Z

formatting changes

Wikiuser: Addition of Spring term text

2014-08-24T17:48:04Z

Addition of Spring term text

Wikiuser: Minor Formatting Changes

2014-08-22T20:34:23Z

Minor Formatting Changes

Wikiuser: Basic grammar corrections and addition of Section titles for Large Update to come.

2014-08-22T15:27:27Z

Basic grammar corrections and addition of Section titles for Large Update to come.

@@ Line 119: / Line 119: @@
 [[File:fast_detector.JPG]]
 Figure 3
@@ Line 156: / Line 157: @@
 [[File:Power_Curve.JPG]]
 Figure 7
 Once we had the curve in Figure 7, we drove the laser with as little current as we could to ensure the beam profiler wouldn't be saturated. According to the maunual, the profiler ould handle up to a watt of of average power, but we drove it at 50mW. Figure 8 below shows the output laser before being put through a lens.
-[[File:3d_Profile.JPG]]
+[[File:3d_Profile.jpg]]
 Figure 8
@@ Line 168: / Line 170: @@
 [[File:M_2.JPG]]
-Figure 8
+Figure 9
 This test shows we have a Gaussian beam with an M_2 of approximately 1, with a beam diameter of 3.701 mm. These characterizations can be very useful to any group who takes over the project, for the smaller the beam waist, the higher the power per unit area. Adding a condensing lens system would be a great way to increase the Irradiance.

@@ Line 152: / Line 152: @@
 === Beam Profiler: ===
-After determining that the autocorrelator would not yield the result we wanted, we decided to move on to the beam characterization using a Thorlabs BP209-IR and a translation stage for use as an M_2 tool. The same two mirror setup used with the autocorrelator was used to align the beam profiler. Figure 7 below shows the output laser before being put through a lens.
+After determining that the autocorrelator would not yield the result we wanted, we decided to move on to the beam characterization using a Thorlabs BP209-IR and a translation stage for use as an M_2 tool. The same two mirror setup used with the autocorrelator was used to align the beam profiler. Before the system was safe to run through a beam profiler, an accurate measure of output power vs drive current had to be determined to ensure it would be known exactly how much power would be sent into the profiler. Figure 7 below shows the determined output power vs drive current curve.
-Figure 7
+[[File:3d_Profile.JPG]]
-A 200mm lens was then placed in front of the beam profiler and an M_2 measurement was taken. Figure 8 below shows the results of the M_2 test.
+A 200mm lens was then placed in front of the beam profiler and an M_2 measurement was taken. Figure 9 below shows the results of the M_2 test.
 [[File:M_2.JPG]]

@@ Line 104: / Line 104: @@
+[[File:HPPFLS.JPG]]
 Figure 1
@@ Line 131: / Line 131: @@
 [[File:Autocorrelator.JPG]]
-Figure 4
+[[File:Output_Coupler.JPG]]

@@ Line 112: / Line 112: @@
 With every connector removed, the output power at 0.67 amps on each pump became 117 mW (or 120 mW at 0.7 A each). This was more than enough to run the autocorrelator. Yet before we had access to the autocorrelator, we used a pair of fast photodiodes to determine the repetition rate of the laser. When using the slowest detector we got the waveform below in Figure 2.
-[[File:slow_detector.jpg]]
+[[File:slow_detector.JPG]]
 Figure 2
@@ Line 118: / Line 118: @@
 This waveform had pulses every 14.4 ns, but the pulse width itself was so large due to the bandwidth limit of the detector. So once a faster detector was acquired, we hooked it up and saw the image in Figure 3 below
-[[File:fast_detector.jpg]]
+[[File:fast_detector.JPG]]
 Figure 3
@@ Line 142: / Line 142: @@
 According to the Autocorrelator, the output signal on the detector should appear like Figure 6. The first step represents the a DC offset in the detector, the second step is remnants of first harmonic getting through, and the peak on top is the second harmonic generation. To calculate the pulse width of the laser, the width of the second harmonic is put over the space between pulses (200 ms) and multiplied by 360 (degrees), a constant K (3.80 ps/degree) and a Gaussian coefficient 0.707. When we ran the signal through the system we got the signal below in Figure 6.
-[[File:ifsignal.jpg]]
+[[File:ifsignal.JPG]]
 Figure 6
@@ Line 160: / Line 160: @@
 A 200mm lens was then placed in front of the beam profiler and an M_2 measurement was taken. Figure 8 below shows the results of the M_2 test.
-[[File:M_2.jpg]]
+[[File:M_2.JPG]]
 Figure 8

@@ Line 112: / Line 112: @@
 With every connector removed, the output power at 0.67 amps on each pump became 117 mW (or 120 mW at 0.7 A each). This was more than enough to run the autocorrelator. Yet before we had access to the autocorrelator, we used a pair of fast photodiodes to determine the repetition rate of the laser. When using the slowest detector we got the waveform below in Figure 2.
-[[File:slow detector.jpg]]
+[[File:slow_detector.jpg]]
 Figure 2
@@ Line 118: / Line 118: @@
 This waveform had pulses every 14.4 ns, but the pulse width itself was so large due to the bandwidth limit of the detector. So once a faster detector was acquired, we hooked it up and saw the image in Figure 3 below
+[[File:fast_detector.jpg]]
 Figure 3
 This image also has a repetition rate of 14.4 ns from large peak to large peak, which made us confident in an actual repetition rate of 14.4 ns. Its pulses were measured at 460ps, which was also the bandwidth of the fast detector. Since we were right at the bandwidth of the detector, we felt it was safe to assume the actual pulses were considerably faster. In order to determine exactly how fast, we would need an autocorrelator.
@@ Line 129: / Line 127: @@
 === Autocorrelator: ===
-In order to hook up the Minioptic Technology Miniscan Autocorrelator, a set of coupling mirrors were needed. Figure 4 below shows the output coupler used to align the autocorrelator (and the M_2 tool used later).
+In order to hook up the Minioptic Technology Miniscan Autocorrelator, a set of coupling mirrors were needed. Figure 5 below shows the output coupler used to align the autocorrelator (and the M_2 tool used later).
 [[File:Autocorrelator.JPG]]
@@ Line 135: / Line 133: @@
 Figure 4
 According to the Autocorrelator, the output signal on the detector should appear like Figure 6. The first step represents the a DC offset in the detector, the second step is remnants of first harmonic getting through, and the peak on top is the second harmonic generation. To calculate the pulse width of the laser, the width of the second harmonic is put over the space between pulses (200 ms) and multiplied by 360 (degrees), a constant K (3.80 ps/degree) and a Gaussian coefficient 0.707. When we ran the signal through the system we got the signal below in Figure 6.
 Figure 6
@@ Line 159: / Line 160: @@
 A 200mm lens was then placed in front of the beam profiler and an M_2 measurement was taken. Figure 8 below shows the results of the M_2 test.
 Figure 8

← Older revision		Revision as of 18:20, 24 August 2014
Line 131:		Line 131:
	In order to hook up the Minioptic Technology Miniscan Autocorrelator, a set of coupling mirrors were needed. Figure 4 below shows the output coupler used to align the autocorrelator (and the M_2 tool used later).		In order to hook up the Minioptic Technology Miniscan Autocorrelator, a set of coupling mirrors were needed. Figure 4 below shows the output coupler used to align the autocorrelator (and the M_2 tool used later).

		+	[[File:Autocorrelator.JPG]]

	Figure 4		Figure 4

@@ Line 83: / Line 83: @@
 . Resolve the Q-Switching problem and achieve Mode-Locke pulses.
 . Optimize the power such that there’s enough average power for an autocorrelator (at least 50mW).
 B. Create a Power characterization chart when optimized.
 . Replace connectors with Fusion Splices.
 . Replace ER-80 with ER-30
 . Determine beam characteristics of the pulse
 . Determine the pulse width and by extension peak power.
@@ Line 106: / Line 112: @@
 With every connector removed, the output power at 0.67 amps on each pump became 117 mW (or 120 mW at 0.7 A each). This was more than enough to run the autocorrelator. Yet before we had access to the autocorrelator, we used a pair of fast photodiodes to determine the repetition rate of the laser. When using the slowest detector we got the waveform below in Figure 2.
 Figure 2
@@ Line 164: / Line 171: @@
 . Beam Type: Gaussian
 . M_2: 0.98
 . Beam Diameter: 3.701 mm
 . Repetition Rate: 14.4 ns
 . Average Power: 120 mW
 . Pulse Width*: 36.75 ps
 . Peak Power: 47.02 W
-*The pulse width is the finest width that could be determined while using the autocorrelator, but is in fact not the actual pulse width which we believe to be in the femtosecond range.
+**The pulse width is the finest width that could be determined while using the autocorrelator, but is in fact not the actual pulse width which we believe to be in the femtosecond range.
 === Moving Forward: ===
- For any group wishing to take over this project, we have a few suggestions on how to quickly bring the system back to optimal as well as where to focus. To get the system optimized, the polarization controllers need to be adjusted and the power needs to be watched. Using a free space power meter at either the output or the 1% tap of the fiber coupler, the polarization controllers can be slowly adjusted to maximize power to the output. If both pumps are on at 0.67 A, then the output power should be 117mW when optimized.
+For any group wishing to take over this project, we have a few suggestions on how to quickly bring the system back to optimal as well as where to focus. To get the system optimized, the polarization controllers need to be adjusted and the power needs to be watched. Using a free space power meter at either the output or the 1% tap of the fiber coupler, the polarization controllers can be slowly adjusted to maximize power to the output. If both pumps are on at 0.67 A, then the output power should be 117mW when optimized.
 If any fusion splices need to be redone, we recommend taping them to a flat post bolted to the table to keep them from moving.

@@ Line 79: / Line 79: @@
 === Goals: ===
 === Setup: ===
@@ Line 88: / Line 122: @@
 === Autocorrelator: ===
 === Beam Profiler: ===
 === Final Results: ===
 === Moving Forward: ===

@@ Line 2: / Line 2: @@
 = HPPFL: Gerald Buxton, Jacob Megors, Nick Kouri, and David Raschko  =
+== Spring ==
   Gerald Buxton and Jacob Megors
 In fiber lasers, the active gain medium is an optical fiber that is doped with a rare earth element. In our laser, this element is erbium. However, other elements such as ytterbium, dysprosium, and thulium can be used. The development of fiber lasers has proved an influential component in terms of both advancement and application.  For example, fiber as an optical path allows for a durable, transportable, and convenient physical apparatus. In addition, fiber properties allow for a high optical quality, while also making it easy to couple light. They allow us to achieve much greater power than otherwise, up to thousands of kW.
@@ Line 18: / Line 18: @@
-== Our Set Up: ==
+=== Our Set Up: ===
@@ Line 24: / Line 24: @@
 [[File:Setup.png|600px]]
-== Optical Bench Alignment: ==
+=== Optical Bench Alignment: ===
@@ Line 38: / Line 38: @@
-== Address of Goals and Progress: ==
+=== Address of Goals and Progress: ===
@@ Line 75: / Line 75: @@
-= Summer Optimization: =
+== Summer Optimization: ==
   Nick Kouri and David Raschko
-== Goals: ==
+=== Goals: ===
-== Setup: ==
+=== Setup: ===
-== Autocorrelator: ==
+=== Autocorrelator: ===
-== Beam Profiler: ==
+=== Beam Profiler: ===
-== Final Results: ==
+=== Final Results: ===
-== Moving Forward: ==
+=== Moving Forward: ===

@@ Line 1: / Line 1: @@
-== HPPFL: Gerald Buxton and Jacob Megors ==
+= HPPFL: Gerald Buxton, Jacob Megors, Nick Kouri, and David Raschko  =
-Background:
+== Background:==
 In fiber lasers, the active gain medium is an optical fiber that is doped with a rare earth element. In our laser, this element is erbium. However, other elements such as ytterbium, dysprosium, and thulium can be used. The development of fiber lasers has proved an influential component in terms of both advancement and application.  For example, fiber as an optical path allows for a durable, transportable, and convenient physical apparatus. In addition, fiber properties allow for a high optical quality, while also making it easy to couple light. They allow us to achieve much greater power than otherwise, up to thousands of kW.
@@ Line 14: / Line 15: @@
 In general, fiber lasers utilize stimulated emission in order to amplify light, in keeping with the famous LASER acronym (Light Amplification by Stimulated Emission of Radiation). In the process of pumping, the erbium dopant absorbs incident photons and is excited to a higher energy state. Quickly, the erbium is then relaxed to the first excited energy state. In this process, energy is stored and used to amplify the pump signal. For our three level model, the erbium occupies the ground state after each stimulated emission event.
-While many fiber lasers utilize a Fabry-Perot cavity, while ours employs a ring cavity. One advantage of this is that most of the cavity is in fiber.
+While many fiber lasers utilize a Fabry-Perot cavity, ours employs a ring cavity. One advantage of this is that most of the cavity is in fiber.
-Our Set Up:
+== Our Set Up: ==
@@ Line 23: / Line 24: @@
 [[File:Setup.png|600px]]
-Optical Bench Alignment:
+== Optical Bench Alignment: ==
@@ Line 37: / Line 38: @@
-Address of Goals and Progress
+== Address of Goals and Progress: ==
@@ Line 46: / Line 47: @@
 Secondly, we hoped to reproduce the self-pulsing behavior that Dar and David observed over the summer. With our new and improved bench (~80% efficiency, no elements), we were quickly able to reproduce these results. In addition, we developed a plan to overcome the presumed culprits of self-pulsing. Basically, it has been shown that lasers with erbium-doped fibers often display symptoms of self-pulsing operation. For more on the theory behind this, please refer to the (Insert graphs from an illustrator program that we discussed) appropriate section. To overcome this phenomenon, we hope that by adding a second 980 pump we will have enough power to overcome the problem.
-Next, we hoped to develop a method of fusion splicing EDF-80 to SMF-28 to replace the connectorized parts of the cavity. Previously, the laser had seen evidence of back reflections, hopefully due simply to faulty and imperfect connections. With this goal, we hoped to achieve a few things both practical and educational. Firstly, we hoped to better familiarize ourselves with the process of fusion splicing, one that is extremely relevant in industrial settings. In addition, we hoped to develop a consistent method for confronting the problem of EDF to SMF fusion splices. For whatever reason, the LID (Light-Injection Detection) system failed to function properly for this particular splice. As a result, we were unable to known with great certainty how efficient each splice was. We designed a simple factorial design experiment that would allow us to rather simply deduce the correct parameters for a good splice. There were many problems on the way. We hoped to test a series of values for specific parameters (variable on the RXS77), and then characterize the loss. To characterize the loss, we would essentially shine an alignment laser of known power through our spliced fiber, and measure the resultant loss through the connection. These results would be of great value for the lab, as this splice would no longer be an issue of great and unknown concern. We battled many obstacles along the way, but we eventually settled on both procedure and design. We have a new alignment laser that will not be absorbed through EDF. In addition, we were attempting to fusion splice fiber that had non-matching core sizes. We have ordered new fiber and corrected this problem. HWe are in great shape with respect to this goal, and we were able to perform a preliminary fractional factorial design experiment. While the results were not sufficient to deliver a conclusive answer, the experiment was worthwhile. We tested 4 parameters: Autofeed, prefusion time, fusion time, and fusion current. the results are documented below. The table provides the loss measurements for a given splice with the specified parameters.
+Next, we hoped to develop a method of fusion splicing EDF-80 to SMF-28 to replace the connectorized parts of the cavity. Previously, the laser had seen evidence of back reflections, hopefully due simply to faulty and imperfect connections. With this goal, we hoped to achieve a few things both practical and educational. Firstly, we hoped to better familiarize ourselves with the process of fusion splicing, one that is extremely relevant in industrial settings. In addition, we hoped to develop a consistent method for confronting the problem of EDF to SMF fusion splices. For whatever reason, the LID (Light-Injection Detection) system failed to function properly for this particular splice. As a result, we were unable to know with great certainty how efficient each splice was. We designed a simple factorial design experiment that would allow us to rather simply deduce the correct parameters for a good splice. There were many problems on the way. We hoped to test a series of values for specific parameters (variable on the RXS77), and then characterize the loss. To characterize the loss, we would essentially shine an alignment laser of known power through our spliced fiber, and measure the resultant loss through the connection. These results would be of great value for the lab, as this splice would no longer be an issue of great and unknown concern. We battled many obstacles along the way, but we eventually settled on both procedure and design. We have a new alignment laser that will not be absorbed through EDF. In addition, we were attempting to fusion splice fiber that had non-matching core sizes. We have ordered new fiber and corrected this problem. We are in great shape with respect to this goal, and we were able to perform a preliminary fractional factorial design experiment. While the results were not sufficient to deliver a conclusive answer, the experiment was worthwhile. We tested 4 parameters: Autofeed, prefusion time, fusion time, and fusion current. The results are documented below. The table provides the loss measurements for a given splice with the specified parameters.
 The first file below shows the results of the ANOVA we ran. As you can see, the only parameter with a P-Value of less than 0.5 is autofeed. A p-value of 0.5 disproves the null hypothesis for the experiment. In our case, the null hypothesis is that these variables do not effect the quality of the fusion splice.
@@ Line 72: / Line 73: @@
 Finally, we hoped to be able to measure the dispersion of pumped EDF-80. In any final and functional laser, these measurements will be vital for deterring the correct length of EDF to be used. We will not get there this term, but we hope to be in a position to achieve these measurements this summer.