  This note supplements a Reply [1] to a Comment [2] which identified a
fundamental symmetry error we made in the original experimental study of a
photon thermal diode [3]. For thermal specialists, here we provide some
additional details about the thermal estimate originally used to justify
omitting the cold-side thermal collimator, and the reasons for its failure.
  References
  [1]. C. Dames, Z. Chen, C. Wong, S. Lubner, S. Yee, J. Miller, W. Jang, C.
Hardin, A. Fong, and J. E. Garay, "Correspondence: Reply to `The experimental
requirements for a photon thermal diode'". Nature Communications (in press,
2017).
  [2]. B. V. Budaev, "Correspondence: The experimental requirements for a
photon thermal diode". Nature Communications (in press, 2017).
  [3]. Z. Chen, C. Wong, S. Lubner, S. Yee, J. Miller, W. Jang, C. Hardin, A.
Fong, J. E. Garay, and C. Dames, "A photon thermal diode". Nature
Communications 5, 5446 (2014).
