Cut-off wavelength in PCF

[Bijan goudarzi]

How can man extract cut-off wavelength for a photonic crystal fibers? which product oft optiwave is proper for this aim?

[Bijan goudarzi]

Dear Sethi,
Is it possible to design a photonic crystal fiber in OptiFiber?

[Damian Marek]

You would need OptiFDTD for this application. Not necessarily the OptiFDTD simulation engine but the additional software that comes with it, OptiMode. In OptiMode you can construct photonic crystal fibers and simulate the modes that exist. You can also run a parameter sweep to find which wavelength corresponds to cutoff.

Regards

[Dr Rk Sethi]

OptiFiber uses numerical mode solvers and other models specialized to fibers for calculating dispersion, losses, birefringence, and PMD.
KEY APPLICATIONS of OptiFiber :
◦Assess parameters, sensitivities, and tolerances
◦Fiber mode solving of LP or Vector modes by Finite Difference or by Transfer Matrix Methods
◦Analysis of measured fiber profiles from instruments such as the EXFO NR-9200
◦Single mode fiber designs such as Corning SMF-28, dispersion flattened or shifted fibers.
◦Multimode fiber design, such as 50/125 m and 62.5/125 m silica fibers.
◦Visualization of multimode interference patterns with propagation
◦Automatic parameter scanning
◦Fiber Sensor design
◦Calculation of birefringence and PMD from intrinsic or extrinsic perturbations

Please have a look at the post of Damian Marek :
Home » Topics » KNOWLEDGE » Photonic Crystal Fiber [FDTD]
Damian Marek
Question:
I want to simulate the transparency of a photonic crystal fiber. For example, I am trying to design a fiber so that there is a small range of wavelengths that will be able to propagate. Is this an OptiFDTD application?
Answer:
OptiFDTD is, as you suggested, the most suitable software for this purpose. You can define a small section of fiber within the software and calculate the transmission and reflection spectra. You can then define geometrical parameters in your design and perform parameter sweeps to fine tune the fiber spectrum.

[Bijan goudarzi]

Dear Marek,
Follow your tip, I went to design my PCF with optiMODE. I was going to do it base on OptiMode_User_Reference pdf file (section: OptiMode Tutorial 5- Photonic Crystal Fiber and VB script). but the script given by the tutorial return error and cant made the PCF structure. here is the exact script of the tutorial and at the end is the returned error,

‘ Make the hexagonal crystal lattice fibre of
‘ Optics Letters Vol.22 No. 13 p961 (1997)
Option Explicit
WGMgr.DeleteAll
Dim X0,Y0,Nperiods,i,j,YLevel,Pitch,HoleDiameter,x_coord
Dim wg_object, Xdefect, Ydefect, windowsz

windowsz = ParamMgr.EvaluateExpr(“window”)

Nperiods = 9
Pitch = 2.3
X0 = – (Nperiods/2 – 0.5) * Pitch
Y0 = – (Nperiods – 1) * (3)^(0.5) * Pitch / 2.0
HoleDiameter = 0.45 * Pitch

Xdefect = Nperiods
Ydefect = Nperiods

WGMgr.OutputMSG(” Periods = ” & Nperiods & ” Pitch = ” & Pitch & _
” Hole Diameter = ” & HoleDiameter)
‘ Create the lower half of the photonic crysal.
‘ Don’t put a waveguide at i = j = Nperiods
For j = 1 To Nperiods
YLevel = Y0 + (j-1) * (3)^(0.5) * Pitch / 2.0
If YLevel > – windowsz / 2 Then
For i = 1 To Nperiods + j – 1
x_coord = X0 + (i – 1) * Pitch – (j – 1) * Pitch / 2.0
If( (i<>Xdefect Or j<>Ydefect) And x_coord < windowsz / 2 _
And x_coord > – windowsz / 2 ) Then
Set wg_object = WGMgr.CreateObj(“WGLinearXS”, “Hole_”& _
CStr(j)&”_”&CStr(i) )
wg_object.SetStart x_coord, YLevel
wg_object.SetAttr “WidthExpr”, CStr(HoleDiameter)
wg_object.SetProfileName “Hole”
End If
Next
End If
Next

‘ Create the upper half of the photonic crystal
For j = Nperiods + 1 To 2 * Nperiods – 1
YLevel = Y0 + (j-1) * (3)^(0.5) * Pitch / 2.0
If YLevel < windowsz / 2 Then
For i = 1 To 3 * Nperiods – j – 1
x_coord = X0 + (i – 1) * Pitch + (j – 2 * Nperiods + 1) _
* Pitch / 2.0
If x_coord < windowsz / 2 And x_coord > – windowsz / 2 Then
Set wg_object = WGMgr.CreateObj(“WGLinearXS”, “Hole_” _
&CStr(j) &”_”&CStr(i) )

wg_object.SetStart x_coord, YLevel
wg_object.SetAttr “WidthExpr”, CStr(HoleDiameter)
wg_object.SetProfileName “Hole”
End If
Next
End If
Next

VB scripting: ‘Microsoft VBScript runtime error’ Line:25,char:4, ‘Type mismatch: ‘[string: “Error: Unknown varia”]”

*Line 25 is refered to: If YLevel > – windowsz / 2 Then

what is wrong with it?

[Damian Marek]

The error is because you are trying to access a parameter that might not exist in your Functions and Variables, Before running the script go to Solving tab -> Edit Parameters and add the parameters “window” = 25 and “ScanWavelength” = 1.00 the tutorial file has them as well.

Regards

[Ravil]

Agree with Damian, sweep option should give you a cut-off wavelength.

[Author]

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