Volume 15, Issue 4, 15 August 1969
Index of content:
15(1969); http://dx.doi.org/10.1063/1.1652924View Description Hide Description
Data are presented (77°K) showing that laser transitions to either the valence band edge or to the acceptor, or both, are possible in a specific impurity concentration range (2 × 1017−1018/cm3) in GaAs:Zn and GaAs:Cd. These data are observed on a low‐loss crystal structure that is pumped uniformly.
15(1969); http://dx.doi.org/10.1063/1.1652925View Description Hide Description
The paper reports oscillation and doubling of the 0.946‐μ line in Nd3+:YAG. Peak, Q‐switched output powers of approximately 2 kW at 0.473 μ were obtained. The results of a calculation for optimum nonlinear coupling to an internal Q‐switched laser are given.
15(1969); http://dx.doi.org/10.1063/1.1652926View Description Hide Description
The visible afterglow radiation from low‐pressure weakly ionized helium exhibits a partial quenching due to absorption of infrared photons (0.11–0.14 eV). The helium sample is placed in the cavity of a Q‐switched CO2 laser and studied at gas temperatures in the range from 77 to 300°K. The partial quenching appears to originate from photon‐induced change of population of a state or states of a neutral or ionic helium molecule.
15(1969); http://dx.doi.org/10.1063/1.1652927View Description Hide Description
The results of an analysis of the energy transfer and two‐step excitation in LaF3:Yb,Er are presented. The physical model assumes that the Yb3+ and Er3+ ions are tightly coupled and transfer occurs both ways. The simple model used is able to explain the experimentally observed time dependence and radiant efficiency provided one assumes the following decay times: Yb3+(5 F 5/2), 2 msec; Er3+(4 F 7/2), ∼1 μsec; Er3+(4 S 3/2), 0.125 msec.
15(1969); http://dx.doi.org/10.1063/1.1652928View Description Hide Description
A method is described which permits rapid and precise selective etching of silicon crystal surfaces without protecting any part of the surface during the etch procedure. Prior to the etching process the areas to be etched are subjected to an ion‐bombardment treatment, which increases the etch rate in the bombarded surface layer compared to the etch rate of untreated silicon.Etching characteristics for silicon crystals bombarded with neon and argon are presented and shown to agree with theoretical predictions based on a simple model in which the etching characteristics are related to implantation‐produced cluster damage.
15(1969); http://dx.doi.org/10.1063/1.1652929View Description Hide Description
The superfluid He II transition to the normal state and the critical dissipation rates for near‐isothermal solenoid operation have been measured near the λ point. In contrast to the superfluidquenching limit, the solenoid cooling stability limit was found to be finite at the λ point.
15(1969); http://dx.doi.org/10.1063/1.1652930View Description Hide Description
By observing constant‐voltage steps from Josephson junctions at voltages as high as 17 mV we deduce that junctions can generate harmonics up to frequencies as high as 8200 GHz. In consonance with this, submillimeter wave laser detection, harmonic generation, and mixing are demonstrated. These results suggest a model for the upper frequency limit of the Josephson effect.
15(1969); http://dx.doi.org/10.1063/1.1652931View Description Hide Description
Infrared holography at 10.6 μm has been accomplished by using a thermochromic material, cuprous mercuric iodide, to record an on‐axis interference pattern. The pattern is subsequently reduced in a two‐step photographic process, and reconstruction is accomplished in the visible with He–Ne laser light.
15(1969); http://dx.doi.org/10.1063/1.1652932View Description Hide Description
15(1969); http://dx.doi.org/10.1063/1.1652933View Description Hide Description