[mini] Fix grid size calculation in mode decomposition (#297)

Co-authored-by: Parth Ramakant Patil <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

lasy/utils/mode_decomposition.py

@@ -67,15 +67,23 @@ def hermite_gauss_decomposition(laserProfile, n_x_max=12, n_y_max=12, res=1e-6):
         hi[0] = laserProfile.w0 * 5 + laserProfile.x_offset
         hi[1] = laserProfile.w0 * 5 + laserProfile.x_offset
 
-    N_pts_x = int((hi[0] - lo[0]) / res)
-    N_pts_y = int((hi[1] - lo[1]) / res)
+    Nx = int((hi[0] - lo[0]) // (2 * res) * 2) + 2
+    Ny = int((hi[1] - lo[1]) // (2 * res) * 2) + 2
 
     # Define spatial arrays
-    x = np.linspace(lo[0], hi[0], N_pts_x)
-    y = np.linspace(lo[1], hi[1], N_pts_y)
+    x = np.linspace(
+        (lo[0] + hi[0]) / 2 - (Nx - 1) / 2 * res,
+        (lo[0] + hi[0]) / 2 + (Nx - 1) / 2 * res,
+        Nx,
+    )
+    y = np.linspace(
+        (lo[1] + hi[1]) / 2 - (Ny - 1) / 2 * res,
+        (lo[1] + hi[1]) / 2 + (Ny - 1) / 2 * res,
+        Ny,
+    )
     X, Y = np.meshgrid(x, y)
-    dx = x[2] - x[1]
-    dy = y[2] - y[1]
+    dx = x[1] - x[0]
+    dy = y[1] - y[0]
 
     # Get the field on this grid
     field = laserProfile.evaluate(X, Y)
@@ -123,7 +131,7 @@ def estimate_best_HG_waist(x, y, field):
     """
     dx = x[1] - x[0]
     dy = y[1] - y[0]
-    assert dx == dy
+    assert np.isclose(dx, dy, rtol=1e-10)
 
     X, Y = np.meshgrid(x, y)