From c7e823b0b38a455ba604596f69a1b9e165b87b5f Mon Sep 17 00:00:00 2001
From: Jan Petykiewicz <jan@mpxd.net>
Date: Tue, 23 May 2023 12:49:55 -0700
Subject: [PATCH] allow initial value

---
 meanas/fdfd/bloch.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/meanas/fdfd/bloch.py b/meanas/fdfd/bloch.py
index 720fef4..c85b02b 100644
--- a/meanas/fdfd/bloch.py
+++ b/meanas/fdfd/bloch.py
@@ -443,6 +443,7 @@ def find_k(
         k_guess: float | None = None,
         solve_callback: Callable[..., None] | None = None,
         iter_callback: Callable[..., None] | None = None,
+        v0: NDArray[numpy.complex128] | None = None,
         ) -> tuple[float, float, NDArray[numpy.complex128], NDArray[numpy.complex128]]:
     """
     Search for a bloch vector that has a given frequency.
@@ -475,7 +476,7 @@ def find_k(
         k_guess = sum(k_bounds) / 2
 
     n = None
-    v = None
+    v = v0
 
     def get_f(k0_mag: float, band: int = 0) -> float:
         nonlocal n, v