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| Giving P_arm = Plaser *2400. So if Plaser = 10W, Parm = 24kW. |
Giving P_arm = Plaser *2400. So if Plaser = 10W, Parm = 24kW. If we improve T_IMC * T_FI to 90%, then the overall gain becomes x4000, so 10 W from the laser becomes 40 kW in the arms. As to the question "How much power do we need?" I think this depends on the specific configuration we operate in, i.e. SRC detuning and homodyne phase. The general trend which is true is that the optomechanical coupling crosses unity at higher frequencies with higher power. So the frequency at which the IFO quantum noise is at its lowest relative to unsqueezed vacuum is directly proportional to power. We hypothesize that it is easier to measure squeezing at higher frequencies due to lower technical noise. A set of example curves for just the quantum noises is attached. |
Power calculation
P_arm = Plaser * T_PMC * T_IMC * T_FI * alpha_MM * G_PR * T_BS * G_arm
Current best guesses (as of 30 Apr 2019):
- T_PMC = 85%
- T_IMC * T_FI = 50%
- alpha_MM = 98 %
- G_PR = 40 (once we put new folding mirrors in)
- T_BS = 50%
- G_arm = 285 (20 ppm round trip loss)
Giving P_arm = Plaser *2400. So if Plaser = 10W, Parm = 24kW. If we improve T_IMC * T_FI to 90%, then the overall gain becomes x4000, so 10 W from the laser becomes 40 kW in the arms.
As to the question "How much power do we need?" I think this depends on the specific configuration we operate in, i.e. SRC detuning and homodyne phase. The general trend which is true is that the optomechanical coupling crosses unity at higher frequencies with higher power. So the frequency at which the IFO quantum noise is at its lowest relative to unsqueezed vacuum is directly proportional to power. We hypothesize that it is easier to measure squeezing at higher frequencies due to lower technical noise. A set of example curves for just the quantum noises is attached.
- What should our PMC Finesse be so that its barely enough to satisfy filtering reqs and transmission efficiency?
- Suppress angular modes by XX (note that the IMC also filters the beam jitter)
Suppress laser noise at the 11 & 55 MHz readout frequencies by XX (this is primarily a PMC function as the IMC transmits the sidebands)
Maintain a T_PMC > 0.9X (if the existing spec is accurate, the best possible T is ~88%)
- What's up with our T_IMC ?
- let's clean the IMC mirrors
what's the MM frac between PMC and IMC? Judging by the IMC visibility, this is ~98%.
- Is our T_FI too low?
- measure this during the vent when we clean the IMC
- What is the loss in the PRC?
- clipping in the PRC
- new PR/SR mirrors
