Add squeeze module with functions for calculating filter cavity parameters

direct port from MATLAB gwinc

gwinc/squeeze.py

+from numpy import pi, sqrt
+import scipy.constants
+
+def computeFCParams(ifo, fcParams):
+    """Compute ideal filter cavity Tin, detuning [Hz] and bandwidth [Hz]
+
+    """
+    # FC parameters
+    c = scipy.constants.c
+    fsrFC = c / (2 * fcParams.L)
+    lossFC = fcParams.Lrt + fcParams.Te
+  
+    # detuning and cavity bandwidth (D&D paper P1400018 and/or PRD)
+    eps = 4 / (2 + sqrt(2 + 2 * sqrt(1 + (4 * pi * ifo.gwinc.fSQL / (fsrFC * lossFC))**4)))
+    s1eps = sqrt(1 - eps)
+
+    # cavity bandwidth [Hz]
+    gammaFC = ifo.gwinc.fSQL / sqrt(s1eps + s1eps**3)
+    # cavity detuning [Hz]
+    detuneFC = s1eps * gammaFC
+  
+    # input mirror transmission
+    TinFC = 4 * pi * gammaFC / fsrFC - lossFC
+    if TinFC < lossFC:
+        raise RuntimeError('IFC: Losses are too high! %.1f ppm max.' % 1e6 * gammaFC / fsrFC)
+  
+    # Add to fcParams structure
+    fcParams.Ti = TinFC
+    fcParams.fdetune = -detuneFC
+    fcParams.gammaFC = gammaFC
+    fcParams.fsrFC = fsrFC
+
+    return fcParams