Evolution of Temporal Coherence in Confined Exciton-Polariton Condensates.

We study the influence of spatial confinement on the second-order temporal coherence of the emission from a semiconductor microcavity in the strong coupling regime. The confinement, provided by etched micropillars, has a favorable impact on the temporal coherence of solid state quasicondensates that evolve in our device above threshold. By fitting the experimental data with a microscopic quantum theory based on a quantum jump approach, we scrutinize the influence of pump power and confinement and find that phonon-mediated transitions are enhanced in the case of a confined structure, in which the modes split into a discrete set. By increasing the pump power beyond the condensation threshold, temporal coherence significantly improves in devices with increased spatial confinement, as revealed in the transition from thermal to coherent statistics of the emitted light.

Experimental Verification of the Very Strong Coupling Regime in a GaAs Quantum Well Microcavity.

The dipole coupling strength g between cavity photons and quantum well excitons determines the regime of light matter coupling in quantum well microcavities. In the strong coupling regime, a reversible energy transfer between exciton and cavity photon takes place, which leads to the formation of hybrid polaritonic resonances. If the coupling is further increased, a hybridization of different single exciton states emerges, which is referred to as the very strong coupling regime. In semiconductor quantum wells such a regime is predicted to manifest as a photon-mediated electron-hole coupling leading to different excitonic wave functions for the two polaritonic branches when the ratio of the coupling strength to exciton binding energy g/E_{B} approaches unity. Here, we verify experimentally the existence of this regime in magneto-optical measurements on a microcavity characterized by g/E_{B}≈0.64, showing that the average electron-hole separation of the upper polariton is significantly increased compared to the bare quantum well exciton Bohr radius. This yields a diamagnetic shift around 0 detuning that exceeds the shift of the lower polariton by 1 order of magnitude and the bare quantum well exciton diamagnetic shift by a factor of 2. The lower polariton exhibits a diamagnetic shift smaller than expected from the coupling of a rigid exciton to the cavity mode, which suggests more tightly bound electron-hole pairs than in the bare quantum well.

Observation of the Transition from Lasing Driven by a Bosonic to a Fermionic Reservoir in a GaAs Quantum Well Microcavity.

We show that, by monitoring the free carrier reservoir in a GaAs-based quantum well microcavity under nonresonant pulsed optical pumping, lasing supported by a fermionic reservoir (photon lasing) can be distinguished from lasing supported by a reservoir of bosons (polariton lasing). Carrier densities are probed by measuring the photocurrent between lateral contacts deposited directly on the quantum wells of a microcavity that are partially exposed by wet chemical etching. We identify two clear thresholds in the input-output characteristic of the photoluminescence signal which can be attributed to polariton and photon lasing, respectively. The power dependence of the probed photocurrent shows a distinct kink at the threshold power for photon lasing due to an increased radiative recombination of free carriers as stimulated emission into the cavity mode sets in. At the polariton lasing threshold, on the other hand, the nonlinear increase of the luminescence is caused by stimulated scattering of exciton polaritons to the ground state which do not contribute directly to the photocurrent.

Anomalies of a nonequilibrium spinor polariton condensate in a magnetic field.

We observe a strong variation of the Zeeman splitting of exciton polaritons in microcavities when switching between the linear regime, the polariton lasing, and photon lasing regimes. In the polariton lasing regime the sign of Zeeman splitting changes compared to the linear regime, while in the photon lasing regime the splitting vanishes. We additionally observe an increase of the diamagnetic shift in the polariton lasing regime. These effects are explained in terms of the nonequilibrium "spin Meissner effect."

Room temperature polariton light emitting diode with integrated tunnel junction.

We present a diode incorporating a large number (12) of GaAs quantum wells that emits light from exciton-polariton states at room temperature. A reversely biased tunnel junction is placed in the cavity region to improve current injection into the device. Electroluminescence studies reveal two polariton branches which are spectrally separated by a Rabi splitting of 6.5 meV. We observe an anticrossing of the two branches when the temperature is lowered below room temperature as well as a Stark shift of both branches in a bias dependent photoluminescence measurement.

Prototype of a bistable polariton field-effect transistor switch.

Microcavity exciton polaritons are promising candidates to build a new generation of highly nonlinear and integrated optoelectronic devices. Such devices range from novel coherent light emitters to reconfigurable potential landscapes for electro-optical polariton-lattice based quantum simulators as well as building blocks of optical logic architectures. Especially for the latter, the strongly interacting nature of the light-matter hybrid particles has been used to facilitate fast and efficient switching of light by light, something which is very hard to achieve with weakly interacting photons. We demonstrate here that polariton transistor switches can be fully integrated in electro-optical schemes by implementing a one-dimensional polariton channel which is operated by an electrical gate rather than by a control laser beam. The operation of the device, which is the polariton equivalent to a field-effect transistor, relies on combining electro-optical potential landscape engineering with local exciton ionization to control the scattering dynamics underneath the gate. We furthermore demonstrate that our device has a region of negative differential resistance and features a completely new way to create bistable behavior.

Crohn's disease and sarcoidosis: systemic granulomatosis?

We report an unusual case of severe Crohn's disease with involvement of the lung. In 1993 at age 21 a male patient experienced a Helicobacter-negative duodenitis. A routine chest radiograph revealed spotted opacities in the right upper lobe without discomfort and normal pulmonary function except for a reduced diffusion capacity. Bronchoalveolar lavage showed mild lymphocytosis and biopsies from the macroscopically normal bronchi displayed non-caseating granulomas. In 1995 he had symptoms of peptic ulcer disease with a gastric outlet stenosis. He underwent Billroth I resection with only temporary improvement. Three months later the symptoms had recurred and a stenosing inflammatory process of the duodenum was seen on endoscopy suggesting Crohn's disease. A chest radiograph demonstrated infiltrations in parts of the left lung and bronchoalveolar lavage again revealed alveolar lymphocytosis (CD4/CD8 ratio 3.1). Both the gastrointestinal and pulmonary affections responded to corticosteroids but the duodenal stricture had to be resected. The association of Crohn's disease and pulmonary disorders is discussed.

Interstitial lung disease induced by endogenous Candida albicans.

We report on a 64-year old woman with an interstitial lung disease which had characteristics of hypersensitivity pneumonitis. Severe febrile attacks with impairment of ventilation and diffuse poorly defined radiodensities and ground glass opacities on chest x-ray occured repeatedly. Laboratory data showed hypoxemia, leukopenia and circulating Candida albicans (C.a.)-antigen. Bronchoalveolar lavage revealed an increase in neutrophils. Transbronchial biopsies showed lymphocytic alveolitis, bronchiolitis obliterans and epitheloid cell granulomas. IgG and IgA and the lymphocyte proliferation assay were positive with C.a.-antigen. C.a. was detected in the feces. Intradermal skin test with C.a. showed a positive immediate and late phase reaction and inhalative provocation test with C.a.-antigen was positive. After antimycotic treatment the symptoms resolved completely and long-lasting. We conclude that the disease was induced by C.a.-antigen reaching the lungs from the intestinal tract via the bloodstream.

[Severe leukopenia and bone marrow hypoplasia with gelatinous transformation in anorexia nervosa]. / Schwere Leukopenie und Knochenmarkhypoplasie mit gelatinöser Transformation bei Anorexia nervosa.

HISTORY AND ADMISSION FINDINGS: A 26-year-old woman was admitted because of excessive weight loss: her body mass index was 11.3 kg/m (2). She reported an adequate food intake and denied fear of gaining weight. INVESTIGATIONS: The leukocyte count on admission was 2.0/nl. Bone marrow biopsy showed gelatinous bone marrow transformation with hypocellularity. Psychiatric examination and observation of the patient's eating behavior revealed symptoms typical of anorexia nervosa. DIAGNOSIS, TREATMENT AND COURSE: Because of the diagnosis of anorexia nervosa behaviour therapy was started. During the following months the patient continually gained weight. But it took nine months for leukocyte count to be normal, by which time her body mass index had risen to 17.8 kg/m (2). CONCLUSION: Severe weight loss in anorexia nervosa may lead to leukopenia and gelatinous bone marrow transformation. The abnormal leukocyte count can become normal by maintaining body weight within the normal range.

[Chronic cough and pulmonary infiltration]. / Chronischer Husten und pulmonales Infiltrat.

HISTORY: A 56-year-old man complain of chronic cough for 6 months without further clinical problems. The patient was otherwise in good health and showed only a moderate bronchial sound at the left ventral paracordial region. INVESTIGATIONS: Thorax X-ray revealed an infiltrate in the lingula with segmental borders. The CT scan showed air bronchogramms and bilateral more small infiltrates. DIAGNOSIS, TREATMENT, CLINICAL COURSE: Bronchoscopic transbronchial biopsies revealed a BALT-lymphoma. A seven years old chest X-ray showed the lingual infiltrate in nearly the same extension as the current X-ray. Because of the disseminated manifestation, the slow course and the good performance status we did not start a palliative chemotherapy so far. CONCLUSION: Any pulmonary infiltrate which looks like pneumonia must be given a definite diagnosis if there are no clinical signs of infection.

[Liebow's desquamative pneumonia--a separate disease entity or a form of chronic interstitial pneumonia? (author's transl)]. / Die Stellung der Liebowschen Desquamativpneumonie innerhalb der chronischen interstitiellen Pneumonien.

When in 1965 Liebow first described desquamative interstitial pneumonia (DIP) and differentiated it from other types of interstitial pneumonia he believed it to be a separate disease entity. The fact that the observed cases were of a relatively benign nature seemed to confirm this view. However, during the past years there have been reports of cases which took a less benign course; it was also observed that disorders with features similar to DIP could be produced by various exogenous noxae. The question, therefore, arises, whether DIP is, in fact, a separate disease entity or a specific pulmonary reaction to a variety of similarly acting noxae.

[Histomorphological differential diagnosis between occupational and "idiopathic" pulmonary fibroses]. / Histomorphologische Differentialdiagnose zwischen berufsbedingten und "idiopathischen" Lungenfibrosen.

Pulmonary fibroses are terminal stages of exposure to a whole series of very diverse noxae. Both occupational and nonoccupational causes must be distinguished. Finally, there is the large collective category "idiopathic" fibroses. In terms of their systematics, fibroses can be classified in five largegroups. The classification criteria are etiological when the causes are known, and morphological-descriptive in cases of idiopathic fibrosis. Occupational and "idiopathic" fibroses often cannot be distinguished in biopsy material because of their great histomorphological similarity. In such circumstances, the result of further analyses is crucial. For this reason, the possibility that an occupational pulmonary fibrosis is present must also be considered even in "idiopathic" pulmonary fibroses in order to arrange for further analyses such as BAL, ashing and energy-dispersive X-ray analysis to be performed.

Giant osmiophilic lamellated bodies after temporary ischemia of the rat lung.

Following temporary ischemia of the rat lung an atelectasis was observed after resorption of the extravasate. To determine whether changes in osmiophilic lamellated bodies (OLB) precede and perhaps cause the atelectasis the upper lobe of the right lung was in eight white Wistar-rats subjected to temporary ischemia of 10 minutes. The two axial diameters of the intracellular OLB and their precursors were measured on electron micrographs 10 minutes, 60 minutes, 1 day and 2 days after cessation of the ischemia. The mean diameters were compared by statistical methods. Already after 10 minutes the usual elliptic cut surfaces of OLB were found to be more circular presumably because of swelling caused by an osmotic insufficiency of their membranes. After 2 days, the mean diameter of OLB had doubled, while shape and structure stayed normal. At the same time, the small precursor stages were missing. Consequently, we assume that formation of new OLB--represented by small non-lamallated osmiophilic bodies--and the incorporation of lipids into existing lamellar bodies are processes independent of each other. After a short, temporary ischemia only the formation of new osmiophilic bodies seems to be interrupted and this is associated with a quick growth of existing OLB. However, apparently these cannot be excreted in due time. The result could be lack of surfactant, which would account for the postischemic atelectasis.

[Uterine metastases of malignant melanoma]. / Uterine Metastasen maligner Melanome.

Uterine metastases of extragenital malignomas are rarely presented in literature. Malignant melanoma as primary tumour is described more often than can be expected with regard to its relative incidence in comparison to other malignomas. If the uterus is involved in melanoma disease, mostly cervix and myometrium are affected, endometrial metastases are considered to be very rare. If the primary tumour is known, bleeding abnormalities frequently lead to the diagnosis of uterine metastases, but occasionally abnormal bleeding appears to be the first symptom of melanoma disease. In the following another such case is described and an additional case of endometrial metastases of malignant melanoma is presented.

[Cryptococcal sepsis simulating miliary tuberculosis in malignant lymphoma]. / Kryptokokkensepsis unter dem Bild einer Miliartuberkulose bei malignem Lymphom.

A malignant non-Hodgkin lymphoma (Cb-Cc) stage IVb was diagnosed in a man of 71 years of age. He was subjected to polychemotherapy. The mediastinum was irradiated. Cortisone therapy was performed because of irradiation pneumonitis. A highly febrile disease pattern developed with increasing dyspnoea while displaying the signs and symptoms of a miliary pulmonary disease. The treatment course was directed at combatting miliary tuberculosis. The patient died from cardiorespiratory failure. The postmortem examination supplied proof of cryptococcal sepsis. The differential diagnosis is discussed.