Barwood, G P; Gill, P; Klein, H A; Hosaka, K; Huang, G; Lea, S N; Margolis, H S; Szymaniec, K; Walton, B R (2017) Trapped strontium ion optical clocks. Proceedings of the SPIE, 10567. 105672U

Szymaniec, K; Lea, S N; Gibble, K*; Park, S E*; Liu, K*; Glowacki, P* (2016) NPL Cs fountain frequency standards and the quest for the ultimate accuracy. J. Phys.: Conf. Ser., 723. 012003

Godun, R M; Nisbet-Jones, P B R; Jones, J M; King, S A; Johnson, L A M; Margolis, H S; Szymaniec, K; Lea, S N; Bongs, K*; Gill, P (2014) Frequency ratio of two optical clock transitions in 171Yb+ and constraints on the time-variation of fundamental constants. Phys. Rev. Lett., 113 (21). 210801

Parker, B; Marra, G; Johnson, L A M; Margolis, H S; Webster, S A; Wright, L; Lea, S N; Gill, P; Bayvel, P* (2014) Transportable cavity-stabilised laser system for optical carrier frequency transmission experiments. Appl. Opt., 53 (35). pp. 8157-8166.

Szymaniec, K; Lea, S N; Liu, K* (2014) An evaluation of the frequency shift caused by collisions with background gas in the primary frequency standard NPL-CsF2. IEEE Trans. Ultrason. Feroelectr. Freq. Control, 61 (1). pp. 203-206.

Gibble, K*; Lea, S N; Szymaniec, K (2012) A microwave cavity designed to minimize distributed cavity phase errors in a primary cesium frequency standard. In: 2012 Conference on Precision Electromagnetic Measurements (CPEM 2012), 1-6 July 2012, Washington DC, USA.

Marra, G; Slavik, R*; Margolis, H S; Lea, S N; Petropoulos, P*; Richardson, D J*; Gill, P (2011) High resolution microwave frequency transfer over a 86 km-long optical fiber network using a mode-locked laser.. Opt. Lett., 36 (4). pp. 511-513.

Webster, S A; Godun, R; King, S; Huang, G L; Walton, B; Tsatourian, V; Margolis, H S; Lea, S N; Gill, P (2010) Frequency measurement of the S-2(1/2)-D-2(3/2) electric quadrupole transition in a single Yb-171(+) ion. IEEE Trans. Ultrason. Feroelectr. Freq. Control, 57 (3). pp. 592-599.

Marra, G; Margolis, H S; Lea, S N; Gill, P (2010) High-stability microwave frequency transfer by propagation of an optical frequency comb over 50 km of optical fiber. Opt. Lett., 35 (7). pp. 1025-1027.

Lea, S N; Taghavi-Larigani, S*; Burt, E A*; Prestage, J D*; Tjoelker, R L* (2009) A New Trapped Ion Clock Based On 201Hg+. In: European Frequency and Time Forum – International Frequency Control Symposium) EFTF-IFCS Joint Conference 2009, 20-24 April 2009, Besancon, France.

Marra, G; Lea, S N; Margolis, H S; Gill, P (2008) Fibre transfer of high stability microwave references with optical frequency combs. In: 2008 Lasers and Electro-optics and Quantum Electronics and Laser Science Conference, 4-9 May 2008, San Jose, CA, USA.

Margolis, H S; Lea, S N; Walton, B R; Marra, G; Reid, D T*; Gill, P (2008) Improvements to the robustness of a Ti: sapphire-based femtosecond comb at NPL. In: Proceedings of the 7th Symposium on Frequency Standards and Metrology., 5-11 October 2008, Pacific Grove, California, USA.

Lea, S N (2008) Limits to time variation of fundamental constants from comparisons of atomic frequency standards. Eur. Phys. J. Special Topics, 163 (1). pp. 37-54.

Marra, G; Lea, S N; Margolis, H S; Gill, P (2008) Microwave and optical frequency transfer via optical fibre. In: Proceedings of the 7th Symposium on Frequency Standards and Metrology., 5-11 October 2008, Pacific Grove, California, USA.

Lea, S N; Burt, E A*; Prestage, J D*; Taghavi, S*; Tjoelker, R L* (2008) A dual-isotope mercury ion clock to search for variation in fundamental constants. In: 7th Symposium on Frequency Standards and Metrology, 5-11 October 2008, Pacific Grove, California, USA.

Margolis, H S; Barwood, G P; Huang, G; Klein, H A; Lea, S N; Marra, G; Tsatourian, V; Walton, B R; Gill, P (2008) An optical clock based on a single trapped 88Sr+ ion. In: Proceedings of the 7th Symposium on Frequency Standards and Metrology., 5-11 October 2008, Pacific Grove, California, USA.

Lea, S N (2007) Limits to time variation of fundamental constants from comparisons of atomic frequency standards. Rep. Prog. Phys., 70 (9). pp. 1473-1523.

Christodoulia, N; Lea, S N; Marra, G; Margolis, H S; Gill, P; Leburn, C G*; Fusari, F*; Brown, C T A* (2007) Mode-locked lasers for remote intercomparison of frequency standards over optical fibre networks. In: OFMC 2007, 15-17 October 2007, NPL, UK.

Lea, S N; Webster, S A; Barwood, G P (2007) Polarisabilities and blackbody shifts in Sr+ and Yb+. In: Proceedings of the 20th European Frequency and Time Forum, 27-30 March 2006, PTB, Germany.

Hosaka, K; Webster, S A; Stannard, A; Margolis, H S; Lea, S N; Walton, B R; Gill, P (2006) An 171Yb+ optical frequency standard at 467 nm. In: CPEM 2006 Conference on Precision Electromagnetic Measurements, 9-14 July 2006, Torino, Italy.

Hosaka, K; Webster, S A; Stannard, A; Margolis, H S; Lea, S N; Walton, B R; Gill, P (2006) An 171Yb+ optical frequency standard at 467 nm. In: CPEM 2006 Conference on Precision Electromagnetic Measurements, 9-14 July 2006, Torino, Italy.

Edwards, C S; Margolis, H S; Barwood, G P; Lea, S N; Gill, P; Rowley, W R C (2006) Development of a pair of 1.5 micron NICE ohms frequency standards. In: CPEM 2006 Conference on Precision Electromagnetic Measurements, 9-14 July 2006, Torino, Italy.

Walton, B R; Hosaka, K; Lea, S N; Margolis, H S; Gill, P (2006) Optical frequency measurements using femtosecond combs. In: Optical Frequency Combs for Space International Workshop, 2-3 October 2006, NPL, UK.

Szymaniec, K; Chalupczak, W; Whibberley, P B; Lea, S N; Henderson, D (2006) Reply to the comment on 'Evaluation of the primary frequency standard NPL-CsF1'. Metrologia, 43 (3). L18-19

Barwood, G P; Huang, G; Klein, H A; Margolis, H S; Lea, S N; Szymaniec, K; Chalupczak, W; Gill, P (2006) An optical frequency standard based on a transition in a single trapped strontium ion. In: Optical Frequency Combs for Space International Workshop, 2-3 October 2006, NPL, UK.

Lea, S N; Webster, C H; Sinclair, A G; Tzalenchuk, A Ya (2005) Applications of quantum entanglement to metrology. NPL Report. DEM-TQD 005

Szymaniec, K; Chalupczak, W; Whibberley, P B; Lea, S N; Henderson, D (2005) Evaluation of the primary frequency standard NPL-CsF1. Metrologia, 42 (1). pp. 49-57.

Edwards, C S; Margolis, H S; Barwood, G P; Lea, S N; Gill, P; Huang, G; Rowley, W R C (2004) Absolute frequency measurement of a 1.5µm acetylene standard by use of a combined frequency chain and femtosecond comb. Opt. Lett., 29 (6). pp. 566-568.

Edwards, C S; Margolis, H S; Barwood, G P; Lea, S N; Gill, P; Huang, G; Rowley, W R C (2004) Absolute frequency measurements of 1.5 micron acetylene-stabilized lasers. In: Conference on Precision Electromagnetic Measurements (CPEM) 2004, 27 June - 2 July 2004, London, UK.

Margolis, H S; Huang, G; Lea, S N; Barwood, G P; Klein, H A; Gill, P (2004) Comparison of two femtosecond optical frequency combs at NPL. In: Conference on Precision Electromagnetic Measurements (CPEM) 2004, 27 June - 2 July 2004, London, UK.

Szymaniec, K; Chalupczak, W; Whibberley, P B; Lea, S N; Henderson, D (2004) Evaluation of NPL-CSF1 primary frequency standard. In: Conference on Precision Electromagnetic Measurement (CPEM) 2004, 27 June - 2 July 2004, London, UK.

Lea, S N; Huang, G; Margolis, H S; Gill, P (2004) Extending the range and utility of femtosecond combs. In: Conference on Precision Electromagnetic Measurements (CPEM) 2004, 27 June - 2 July 2004, London, UK.

Margolis, H S; Barwood, G P; Huang, G; Klein, H A; Lea, S N; Szymaniec, K; Gill, P (2004) Hertz-level measurement of the optical clock frequency in a single 88Sr+ ion. Science, 306 (5700). pp. 1355-1358.

Lea, S N; Flowers, J L (2004) Proposed laboratory tests of time-variation of the fundamental constants using the ensemble of frequency standards at NPL. In: Conference on Precision Electromagnetic Measurements (CPEM) 2004, 27 June - 2 July 2004, London, UK.

Webster, S A; Hosaka, K; Blythe, P J; Margolis, H S; Lea, S N; Huang, G; Rowley, W R C; Gill, P (2003) Femtosecond comb measurements of the 467 nm electric octupole transition in 171Yb+. NPL Report. CBTLM 28

Margolis, H S; Huang, G; Barwood, G P; Lea, S N; Klein, H A; Rowley, W R C; Gill, P; Windeler, R S* (2003) Absolute frequency measurement of the 674 nm 88Sr+ clock transition using a femtosecond optical frequency comb. Phys. Rev. A, At. Mol. Opt. Phys., 67. 032501

Lea, S N; Rowley, W R C; Margolis, H S; Barwood, G P; Huang, G; Gill, P; Chartier, J.-M*; Windeler, R S* (2003) Absolute frequency measurements of 633 nm iodine-stabilised helium-neon lasers. Metrologia, 40. pp. 84-88.

Blythe, P J; Webster, S A; Margolis, H S; Lea, S N; Huang, G; Choi, S-K; Rowley, W R C; Gill, P; Windeler, R S* (2003) Sub-kilohertz absolute frequency measurement of the 467 nm electric octupole transition in 171Yb+. Phys. Rev. A, At. Mol. Opt. Phys., 67 (2). 020501

Blythe, P J; Webster, S A; Margolis, H S; Lea, S N; Huang, G; Choi, S-K*; Rowley, W R C; Gill, P; Windeler, R S* (2003) Sub-kilohertz absolute frequency measurements of the 467 nm electric octuple transition in 171Yb+. Phys. Rev. A, At. Mol. Opt. Phys., 67. 020501

Margolis, H S; Barwood, G P; Blythe, P J; Gill, P; Hosaka, K; Huang, G; Klein, H A; Lea, S N; Webster, S A (2003) Trapped ion optical Frequency standards and metrology. In: Digest of LEOS Summer Topical Meeting on Photonic Time/Frequency Measurement and Control, 14-16 July 2003, Vancouver, Canada.

Gill, P; Barwood, G P; Klein, H A; Huang, G; Webster, S A; Blythe, P J; Hosaka, K; Lea, S N; Margolis, H S (2003) Trapped ion optical frequency standards. Meas. Sci. Technol., 14 (8). pp. 1174-1186.

Gubin, M*; Kovalchuk, E*; Petrukhin, E*; Shelkovnikov, A*; Tyurikov, D*; Gamidov, R*; Erdogan, C*; Sahin, E*; Felder, R*; Gill, P; Lea, S N; Kramer, G*; Lipphardt, B* (2002) Absolute frequency measurements with a set of transportable He-Ne/CH4 optical frequency standards and prospects for future design and applications. In: Proceedings of the 6th Symposium on Frequency Standards and Metrology, 9-14 September 2001, University of St Andrews, Fife, Scotland, UK.

Lea, S N; Margolis, H S; Huang, G; Barwood, G P; Klein, H A; Blythe, P J; Webster, S A; Rowley, W R C; Gill, P; Windeler, R S* (2002) Femtosecond comb measurements of optical frequency standards at NPL. In: IEEE-LEOS 2002 15th Annual Meeting of the IEEE Lasers and Electo-Optics Society., 10-14 November 2002, Glasgow, UK.

Lea, S N; Margolis, H S; Huang, G; Rowley, W R C; Gill, P; Windeler, R S* (2002) Femtosecond optical frequency comb measurements at NPL. In: 2002 Conference on Precision Electromagnetic Measurements (CPEM), 16-21 June 2002, Ottawa, Canada.

Lea, S N; Margolis, H S; Huang, G; Rowley, W R C; Henderson, D; Barwood, G P; Klein, H A; Webster, S A; Blythe, P; Gill, P (2002) Femtosecond optical frequency comb measurements of lasers stabilised to transitions in 88Sr+, 171Yb+ and I2 at NPL. In: Proceedings of the 6th Symposium on Frequency Standards and Metrology, 9-14 September 2001, University of St Andrews, Fife, Scotland, UK.

Lea, S N; Huang, G; Margolis, H S; Gill, P (2001) Femtosecond laser combs for optical measurement at NPL. In: 15th European Frequency and Time Forum., 2001.

Henderson, D; Lea, S N; Szymaniec, K; Whibberley, P B (2001) Towards a caesium fountain frequency standard at the NPL. In: Proceedings of the 15th European Frequency and Time Forum (EFTF), March 2001, Neuchatel, Switzerland.

Henderson, D; Lea, S N; Szymaniec, K; Whibberley, P B (2001) Towards a ceasium fountain frequency standard at the NPL. In: BEMC 2001- 10th British Electromagnetic Measurement Conference, 6-8 November 2001, Harrogate, UK.

Margolis, H S; Lea, S N; Huang, G; Gill, P (2000) A 3 THz wide optical frequency comb for the NPL methance-to-stontium frequency chain. In: 14th EFTF Conf. Proc., 2000.

Gill, P; Huang, G; Lea, S N; Margolis, H S (2000) An optical frequency chain for absolute frequency measurement of the 445 THz strontium trapped ion frequency standard. In: Conference on Precision Electromagnetic Measurements (CPEM) 2000, 14-19 May 2000, Sydney, Australia.

Whibberley, P B; Henderson, D; Lea, S N (1999) Development of a caesium fountain primary frequency standard at the NPL. In: Proc. 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symposium, 13-16 April 1999, Besancon, France.

Lea, S N; Huang, G; Margolis, H S; Macfarlane, G M; Taylor, P; Gill, P (1999) Optical frequency synthesis in the near IR with application to trapped ion standards. In: Proc. 1999 Joint Meeting of the European Frequency and Time Forum and the IEEE International Frequency Control Symp., 13-16 April 1999, Besancon, France.

Lea, S N; Macfarlane, G M; Gill, P (1999) Progress towards an optical frequency chain at NPL. IEEE Trans. Instrum. Meas., 48 (2). pp. 578-582.

Henderson, D; Whibberley, P B; Szymaniec, K; Lea, S N (1999) Towards a caesium fountain frequency standard at NPL. In: BEMC 99 - 9th International Conference on Electromagnetic Measurement, November 1999, Brighton, UK.

Lea, S N; Macfarlane, G M; Huang, G; Gill, P (1998) Progress towards an optical frequency chain at NPL. In: CPEM '98 Conference on Precision Electromagnetic Measurements Conference Digest, 6-10 July 2003, Washington DC, USA.

Zucco, M*; Dudle, G*; Webb, C*; Whibberley, P B; Lea, S N; Henderson, D (1997) Current progress with the NPL caesium fountain frequency standard. In: Proc. EFTF 97, European Frequency and Time Forum, 4 - 6 March 1997, Neuchatel, Switzerland.

Lea, S N; Gill, P (1996) Proposed infra-red to visible frequency chain at NPL. In: Proc. Fifth symposium on Frequency Standards and Metrology, 1996, Singapore.

Whibberley, P B; Henderson, D; Lea, S N; Zucco, M* (1995) The Caesium Fountain: progress towards the new primary frequency standard at NPL. In: BEMC 95 7th British Electromagnetic Measurements Conference Digest, 6 - 9 November 1995, Malvern.