(a) providing a first electrode, wherein said first electrode is optically transparent;

(b) providing a second electrode that is electrically isolated from said first electrode, wherein said second electrode is or contains an atom reservoir for first metal ions;

(c) providing an ion conductor interposed between said first electrode and said second electrode, wherein said ion conductor is capable of transporting second metal ions, wherein said ion conductor is in contact with said first electrode and with said second electrode, and wherein said ion conductor is optically transparent;

(d) providing a transparent window support in contact with said ion conductor, wherein said transparent window support is optically transparent, wherein said transparent window support, said ion conductor, said first electrode, and said second electrode collectively form an electrochemically cleanable window, and wherein said electrochemically cleanable window is transparent;

(e) exposing said electrochemically cleanable window to a metal vapor, wherein during said exposing, at least some of said metal vapor adsorbs and/or condenses on a surface of said electrochemically cleanable window to generate adsorbed and/or condensed metal vapor, and wherein said adsorbed and/or condensed metal vapor reduces transparency of said electrochemically cleanable window; and

(f) applying a voltage between said first electrode and said second electrode, thereby removing some or all of said adsorbed and/or condensed metal vapor from said electrochemically cleanable window.