It all stared as a final project in nonlinear optics class. Each group of students were assigned a project that applied to what they learned in class to an interesting question. One group was given the task to investigate whether or not cascading, the use of two lower-order nonlinearities to mimic a higher-order one, could be used to beat the fundamental limits. When I was first asked this question by a colleague, I responded in the negative based on the fact that my calculations were general, and applied to a pair of molecules that interact through cascading as well as to a single molecule.
However, upon reflection, I wondered if we could learn something new while studying this process. To get to the punchline, we found that cascading does not break the limit. However, what started as an average-length paper grew into two huge papers. As often happens, our first calculation missed an important case, which presented an assortment of issues that each required deep thought. In the end, we learned a great deal that we felt was of sufficient significance to warrant publication in the Physics Review.
We sent the papers to Physical Review A, and waited. Because our papers are complex, the journal had difficulty finding multiple qualified reviewers. Instead, they chose a highly distinguished individual (we believe that we know his identity based on the style and tone of the review), who reviewed the two papers together. The review started off a bit negative,
"These two manuscripts form a series devoted to the theoretical analysis of the contribution of cascading to second hyperpolarizability of molecules. Cascading is for sure a very interesting phenomenon in non linear optics, far from being well understood and easy to rationalize, and therefore the effort made by Kuzyk and co-workers is for sure welcome. Nevertheless, after reading the two manuscripts, having appreciated the mastering of the microscopic theory for the limit cases studied, with all the approximations involved, I am not sure that I have discovered something either new or unexpected applying to the real world. To be more precise, I am not sure I was given a clue of why experiment on real molecules behaves as it does."
The next paragraph offered that, "The papers report a nice theoretical study, well written and also entertaining of some very very special cases (point like molecules, with one-dimensional symmetry, interacting only in very special arrangements, and with many other approximations) with no direct (at least transparent) insight into the complicacies of real systems...," followed by some detailed criticisms.
The review concluded with, "Now, to make a long story short. The papers are in my view publishable, since the science is solid, the topic is interesting and the general field of research relevant. In order to enhance the chance that these papers do not remain nice case studies of academic interest, the authors should in my view..."
Since the reviewer brought up some valid points, we made extensive revisions to address each and every point, at times developing new and more general theories and running more simulations. The size of the papers grew, but I beleive that the final product is much improved.
The reviewer and the editor agree. This morning, we got an email that opened with: "We are pleased to inform you that your manuscript has been accepted for publication as a Regular Article in Physical Review A. We would also like to bring the appended referee comments to your attention," which reads, "I am fully satisfied with the changes made by the authors. I believe that the papers convey now the information much more efficiently. I have no further comments."
Congratulations to Nathan, Ben, and Jennie for a job well done! Ironically, these papers were accepted on the day of Nathan's wedding. What a great present!