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2 mirror cavity high power experiments, posted by Xinyi Lu at Optical room about lasers and optics

high-power experiments of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics

high-power experiments of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics

high-power experiments of 2-mirror cavity, posted by Xinyi Lu at Optical room about lasers and optics 6x

Message ID: 221 Entry time: Thu May 16 18:51:17 2024 In reply to: 220 Reply to this: 222

Author:	Xinyi Lu
Status:	Fixed
Type:	info
Category:	lasers and optics
Location:	Optical room
Title:	high-power experiments of 2-mirror cavity

here is a Matlab code to try to optimize the telescope for a hot cavity,
taking into account the thermal lens in the coupling mirror.

from that code, one can deduce using the "Gaussian Beam" software (using the attached xml file) an optimized telescope with 100% geometrical coupling @ Pcav = 700kW and absorption in the coatings = 0.6ppm

Xinyi Lu wrote:

Today, Ronic, Daniele and I redo the high-power 2-mirror cavity experiments, and the results are shown in the table (Figure 1 and Excel 2 ).

- The intracavity power ~500kW can be obtained at 47W injection, but we then have no increase or even a decrease in intracavity power when increasing the injection power, and the coupling is decreasing. It looks like the saturation power of the current device.

- We moved the telescope last week at 2A by moving the concave lens 0.5cm closer to the cavity but almost no change in intracavity power (195kW to 193kW). The telescopes for today's experiment are in the new locations from last week, and we didn't move them today.

- Figure 3 shows the locking curve at 500kW with some thermal effect changes.

- Figure 4 shows the de-lock and to-lock curves at 14kW.

- The current results may be due to two causes, the thermal lensing effect and the physical change in the mirror coating. It is possible that the transmission of the two mirrors changes with temperature.

- The next plan is to adjust the telescope at 4A to see if we can increase the intracavity power. Meanwhile, do some simulations about dynamic locking, coupling rate, and transmittance.

Xinyi Lu wrote:

Today, Ronic and I recorded some intracavity power and cavity mode size as shown in Fig. 1.

Coupling was calculated using the locking curve of this overcoupled cavity. Pr/Pi = 1-Cgeo*Cimp, Cimp = 1-|1-2T1/RTL|^2

We can see that the effective gain, coupling, and mode size decrease with increasing power. And the beam is constantly moving.

Tomorrow we will try to optimize the telescope for the high-power hot cavity.

Attachment 1:

telescope_optimization_for_700kW.pdf 425 kB

Attachment 2:

2_Mirrors_-_216MHz_-_700kW_cavity_setup.xml 2 kB | Hide | Hide all | Show all

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE gaussianBeam>
<gaussianBeam version="1.1">
    <bench id="0">
        <wavelength>1.03e-06</wavelength>
        <leftBoundary>0</leftBoundary>
        <rightBoundary>3</rightBoundary>
        <targetBeam id="0">
            <position>1.884</position>
            <waist>0.0005927</waist>
            <positionTolerance>0.1</positionTolerance>
            <waistTolerance>0.01</waistTolerance>
            <minOverlap>0.98</minOverlap>
            <overlapCriterion>0</overlapCriterion>
        </targetBeam>
        <beamFit id="0">
            <name>Fit0</name>
            <dataType>1</dataType>
            <color>4278190335</color>
            <data id="0">
                <position>0</position>
                <value>0</value>
            </data>
            <data id="1">
                <position>0</position>
                <value>0</value>
            </data>
            <data id="2">
                <position>0</position>
                <value>0</value>
            </data>
        </beamFit>
        <opticsList>
            <inputBeam id="2">
                <waist>0.0001447</waist>
                <index>1</index>
                <M2>1</M2>
                <position>0.189</position>
                <name>w0</name>
                <absoluteLock>1</absoluteLock>
            </inputBeam>
            <lens id="5">
                <focal>0.25</focal>
                <position>1</position>
                <name>L3</name>
                <absoluteLock>0</absoluteLock>
            </lens>
            <lens id="6">
                <focal>-0.15</focal>
                <position>1.25</position>
                <name>L4</name>
                <absoluteLock>0</absoluteLock>
            </lens>
            <lens id="11">
                <focal>0.457</focal>
                <position>1.979</position>
                <name>L4</name>
                <absoluteLock>1</absoluteLock>
            </lens>
            <dielectricSlab id="8">
                <indexRatio>1</indexRatio>
                <width>0.01</width>
                <position>1.979</position>
                <name>D2</name>
                <absoluteLock>1</absoluteLock>
            </dielectricSlab>
            <dielectricSlab id="7">
                <indexRatio>1</indexRatio>
                <width>0.01</width>
                <position>2.6708</position>
                <name>D1</name>
                <absoluteLock>1</absoluteLock>
            </dielectricSlab>
        </opticsList>
    </bench>
    <view id="0" bench="0">
        <horizontalRange>3</horizontalRange>
        <verticalRange>0.009999</verticalRange>
        <origin>0</origin>
        <showTargetBeam id="0">1</showTargetBeam>
    </view>
</gaussianBeam>

Attachment 3:

cavity_2M_dynamic_thermal_effect.m 4 kB | Show | Hide all | Show all

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