Find in Library

Uniform arrays of three shapes (<inline-formula><math display="inline"><semantics><mrow><mi>g</mi><mi>a</mi><mi>u</mi><mi>s</mi><mi>s</mi></mrow></semantics></math></inline-formula>, <inline-formula><math display="inline"><semantics><mrow><mi>h</mi><mi>a</mi><mi>t</mi></mrow></semantics></math></inline-formula>, and <inline-formula><math display="inline"><semantics><mrow><mi>p</mi><mi>e</mi><mi>a</mi><mi>k</mi></mrow></semantics></math></inline-formula>) of GaAs microlenses (MLs) by wet-etching are demonstrated, ∼200 nm spatial isolation of epitaxial single QDs embedded (<inline-formula><math display="inline"><semantics><mi>λ</mi></semantics></math></inline-formula>: 890–990 nm) and broadband (<inline-formula><math display="inline"><semantics><mrow><mo>Δ</mo><mi>λ</mi><mo>∼</mo><mn>80</mn></mrow></semantics></math></inline-formula> nm) enhancement of their quantum light extraction are obtained, which is also suitable for telecom-band epitaxial QDs. Combined with the bottom distributed Bragg reflector, the <inline-formula><math display="inline"><semantics><mrow><mi>h</mi><mi>a</mi><mi>t</mi></mrow></semantics></math></inline-formula>-shaped ML forms a cavity and achieves the best enhancement: extraction efficiency of 26%, Purcell factor of 2 and single-photon count rate of <inline-formula><math display="inline"><semantics><mrow><mn>7</mn><mo>×</mo><msup><mn>10</mn><mn>6</mn></msup></mrow></semantics></math></inline-formula> counts per second at the first lens; while the <inline-formula><math display="inline"><semantics><mrow><mi>g</mi><mi>a</mi><mi>u</mi><mi>s</mi><mi>s</mi></mrow></semantics></math></inline-formula>-shaped ML shows a broader band (e.g., longer <inline-formula><math display="inline"><semantics><mi>λ</mi></semantics></math></inline-formula>) enhancement. In the MLs, single QDs with featured exciton emissions are observed, whose time correlations prove single-photon emission with multi-photon probability <inline-formula><math display="inline"><semantics><mrow><msup><mi>g</mi><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></msup><mrow><mo>(</mo><mn>0</mn><mo>)</mo></mrow><mo>=</mo><mn>0.02</mn></mrow></semantics></math></inline-formula>; some QDs show both biexciton <inline-formula><math display="inline"><semantics><mrow><mi>X</mi><mi>X</mi></mrow></semantics></math></inline-formula> and exciton <i>X</i> emissions and exhibit a perfect cascade feature. This work could pave a step towards a scalable array of QD single-photon sources and the application of QD photon-pair emission for entanglement experiments.