Generic Bend

[Douglas]

Hi,

I am having issues to use the generic_bend module.

when using angled output and input waveguides, I see problems on the output GDS. Is there a way to upload images on this forum? I did not find it…

My code is below.

Thanks!

Doug

__________________________________________________

import nazca as nd
import nazca.generic_bend as gb

#=============================================================================
# Connecting bent waveguides
#=============================================================================

# Defining bends
bend1=nd.bend(radius=10,angle=-30 ,width=2).put(0,0)
b = nd.strt(length=1,width=2).put(70,0)
bend2=nd.bend(radius=10,angle=30,width=2).put(b.pin['a0'])

# Generic bend connection
xya = nd.diff(bend1.pin['b0'],nd.Node.rotate(bend2.pin['b0'],180))
A, B, L, Rmin = gb.gb_coefficients(xya,Rin=30, Rout=30) # Curve parameters
xy = gb.curve2polyline(gb.gb_point,xya,0.000001, (A, B, L)) # Curve points
nd.Polyline(layer=10,width=2,points=xy).put(bend1.pin['b0'])

#=============================================================================
# Connecting straight waveguides
#=============================================================================

# Defining straights
straight1 = nd.strt(length=10 , width=2).put(0,20)
straight2 = nd.strt(length=10, width=2).put(60,40)

# Generic bend connection
xya = nd.diff(straight1.pin['b0'],nd.Node.rotate(straight2.pin['a0'],180))
A, B, L, Rmin = gb.gb_coefficients(xya,Rin=30, Rout=30) # Curve parameters
xy = gb.curve2polyline(gb.gb_point,xya,0.000001, (A, B, L)) # Curve points
nd.Polyline(layer=10,width=2,points=xy).put(straight1.pin['b0'])

nd.export_gds(filename='issue1.gds')

[Ronald]

Dear Douglas,

I’ll have to check how you can add an image. I see I have that option.

As for the syntax, note you never need to use the Node class directly:

# works
xya = nd.diff(bend1.pin['b0'], nd.Node.rotate(bend2.pin['b0'], 180))

# but this is shorter and more direct:
xya = nd.diff(bend1.pin['b0'], bend2.pin['b0'].rot(180))

As for the generic bend. Use it with care as it is a more or less intended as an internal function for the ‘pcurve’ (parametric curve). The mechanism can be reused for other types of parameteric curves.

First a path is created, and that is what you export in your example. However, the path’s discretization is not well defined, e.g. if you send it to a foundry. Therefore, there is a nd.util.polyline2polygon method which takes care of the discretization and creating a polygon first. A tutorial on this topic would be helpful.

Ronald

[Xaveer]

Dear Douglas,

Your approach is much more complex (and error prone) than it needs to be. You better use the interconnect module to provide you with a pcurve connection.

Here is how it can be used for your problem:

import nazca as nd
import nazca.generic_bend as gb

# Define interconnect
myIC = nd.interconnects.Interconnect(radius=10, width=2, layer=10)

# Defining bends
bend1 = nd.bend(radius=10, angle=-30, width=2).put(0,0)
b = nd.strt(length=1, width=2).put(70,0)
bend2 = nd.bend(radius=10, angle=30, width=2).put(b.pin['a0'])

myIC.pcurve_p2p(bend1.pin['b0'], Rin=10, Rout=10).put()

# Defining straights
straight1 = nd.strt(length=10, width=2).put(0,20)
straight2 = nd.strt(length=10, width=2).put(60,40)

myIC.pcurve_p2p(straight1.pin['b0'], straight2.pin['a0']).put()

nd.export_gds(filename='no_issue1.gds')

Also note that the radius (Rin,Rout) you specify in the pcurve_p2p() function need to match the radius of the curves you connect to (with the proper sign).

Xaveer

[Douglas]

Thanks Ronald and Xaveer! All working now!

Thanks for the tip Xaveer, will do that way now. I have a special affection to the generic_bend module, that’s why I started working directly from it =).

Regards,

Doug

 

 

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