“…Note, that methods devised in [1][2] have two deficiencies: 1) calculations requires high memory cost, 2) it is not clear how to extend these methods to non-linear case. Similar to [2] but free of noted deficiencies approach was developed in [3][4]. It is common knowledge that two-mirror dispersionless optical resonators are calculated effectively by the Fox-Li roundtrip operator technique including non-linear case [5].…”