Lateral displacement of the mode axis in a misaligned Porro prism resonator.
The lateral shift of the mode axis in a misaligned Porro prism resonator is analyzed. A method to find the tilted mode axis in a misaligned Porro prism resonator is introduced. Expressions for the displacement of the mode axis are deduced. They predict that the lateral displacement of the mode axis is proportional to the horizontal misalignment angle beta and highly dependent of the prism azimuth angle theta. Experimental results obtained agree well with theory.
Porro prism lasers: a new perspective
Porro prism lasers are insensitive to misalignment caused by, for example, shock and temperature variation, making them useful in field applications, for example in target designation and range-finding systems. This property is a result of the property of Porro prisms that they return a reflected beam parallel to the incident beam, regardless of any tilt on the prism. These lasers are generally used in a marginally stable or unstable configuration for low divergence, but in the stable configuration some interesting kaleidoscope modes can be modelled. In previous work on Porro prism resonators we formulated an analytical method of determining which Porro angles resonate and result in petal output modes, as well as the corresponding number of petals. This work has been verified using a numerical model as well as experimentally. We have developed this work further and have investigated the losses associated with a range of Porro angles as well as the effects of these losses on the resulting modes. We conclude by summarizing the design considerations for Porro prism lasers.
The Invention of the Jewish People
'All modern nation states have a story of their origins, passed down through both official and popular culture, and yet few of these accounts have proved as divisive and influential as the Israeli national myth. The well-known tale of Jewish exile at the hands of the Romans during the first century AD, and the assertion of both cultural and racial continuity through to the Jewish people of the present day, resonates far beyond Israel's borders. Despite its use as a justification for Jewish settlement in Palestine and the project of a Greater Israel, there have been few scholarly investigations into the historical accuracy of the story as a whole. In this bold and ambitious new book, Shlomo Sand shows that the Israeli national myth has its origins in the nineteenth century, rather than in biblical times - when Jewish historians, like scholars in many other cultures, reconstituted an imagined people in order to model a future nation. Sand forensically dissects the official story - and demonstrates the construction of a nationalist myth and the collective mystification that this requires. A bestseller in Israel and France, Shlomo Sand's book has sparked a widespread and lively debate. Should the Jewish people regard themselves as genetically distinct and identifiable across the millennia - or should that doctrine now be left behind and if the myth of the Jewish state is dismantled, could this open a path toward a more inclusive Israeli state, content within its borders?'