Fiedler Vector...............
 

I am performing spectral bisectioning on an unstructured mesh. I get the laplacian matrix and i have to compute the eigenvector corresponding to the 2nd smallest eigenvalue (this is called the Fiedler vector) of this matrix. Can anyone help me find an algorithm/source code which does this.

Note:

1. Matrix is symmetric and highly sparse

2. Only the 2nd smallest eigenpair is required

3. The smallest eigenvector is {1,1,1,1......1} corr. to the eigenvalue 0