Mode Matching - two curve mirrors

• Radius of curvature of mirror R1: R1= 1 m
• Radius of curvature of mirror R2: R2= 1 m (Incoupling side)
• Wavelength: λ= 1542.0 nm
• Length between the resonator mirrors: L= 480 mm
• Beam radius at cavity-waist: w0
• Beam radius at mirror: w1, w2
• Distance between:
  • mirror R1 and mirror R2: L
  • mirror R2/lense 1 and lense 2: X
  • mirror R2/lense 1 and collimatorlense: 600mm - X
    • 600mm (+15mm) = optical way of the incoupling breadboard (450mm) + thickness breadboard (10mm) + distance between breadboard and vacuumchamber (30mm) + distance between vacuumchamber and cavity mirror R2 (130mm)
  • collimatorlense and fiber: 2.75 mm

We used the programm Strahl.exe (@IQ) or STRAHLFP.EXE (@PTB) (same software, but different names).
Step 0: Choose parameter

• Wellenlänge: 1542 nm
• Brechungsindex: 1 (Air)

• Welcher Resonatortyp: linearer Resonator

Step 1: Beam waist calculation from resonator

• Nr. 1: Spiegel 1 with Brennweite 500 mm; Einfallwinkel: 0
• Nr. 2: Abstand 480 mm
• Nr. 3: Spiegel 2 with Brennweite 500 mm; Einfallwinkel: 0

→ Waistradius: 457 µm; Strahlradius on the mirrors: 525.2 µm

Step 2:

• Change Spiegel 2 to Linse 1
  • Brechungsindex: 1.5
  • Brennweite: -2000 mm

Step 3:

• Nr. 4: Abstand with Variable X
• Nr. 5: Linse 2 with Variable Y
• Nr. 6: Abstand 600 - X
• Nr. 7: Linse 3 with Brennweite 2.75 mm
• Nr. 8: Abstand 2.75 mm

• Zielwaist: 5.2 µm

Step 4: Playing with the parameters X and Y for the best Überlapp

Case: Mirror R2/lense 1 and collimatorlense: 600mm - X

Case: Mirror R2/lense 1 and collimatorlense: 615mm - X

Step 5: Check what is happend for the wavelength 1560 nm

No effect!