Generation of coherent states of photon-added type via pathway of eigenfunctions

We obtain and investigate the regular eigenfunctions of simple differential operators x(r) d(r+1)/dx(r+1), r = 1, 2,..., with the eigenvalues equal to 1. With the help of these eigenfunctions, we construct a non-unitary analogue of a boson displacement operator which will be acting on the vacuum. In this way, we generate collective quantum states of the Fock space which are normalized and equipped with the resolution of unity with the positive weight functions that we obtain explicitly. These states are thus coherent states in the sense of Klauder. They span the truncated Fock space without first r lowest-lying basis states: |0 >, |1 >,..., |r - 1 >. These states are squeezed, sub-Poissonian in nature and reminiscent of photon-added states in Agarwal and Tara (1991 Phys. Rev. A 43 492).